Free NEET Physics multiple-choice questions on Ohm's Law & Resistivity. Attempt each question and reveal the answer with a full explanation.
The resistance of a wire is R . If it is melted and stretched to n times its original length, its new resistance will be: n 2 R R/n 2 nR R/n Three copper wires of lengths and cross-sectional areas are (L, A) , (2L, A/2) , and (L/2, 2A) . Resistance is minimum in: Wire of length L/2 , area 2A Wire of length L , area A Wire of length 2L , area A/2 All have same resistance A resistor of 1 k has a power rating of 0.5 W . What is the maximum steady current it can carry without being damaged? 22.36 mA 0.5 mA 500 mA 22.36 A A wire of resistance R is stretched to 0.1 % of its original length. The percentage change in its resistance is: 0.2% 0.1% 0.01% 1% Three bulbs of 40 W, 60 W, and 100 W are connected in series to a 220 V source. Which bulb will glow the brightest? 40 W bulb 60 W bulb 100 W bulb All will glow with same brightness Two batteries, one of emf 18 volts and internal resistance 2 and the other of emf 12 volt and internal resistance 1 , are connected as shown. The voltmeter V will record a reading of. 18 volt 30 volt 14 volt 15 volt Power dissipated across the 8 resistor in the circuit shown here is 2 watt. The power dissipated in watt units across the 3 resistor is:- 2.0 1.0 0.5 3.0 The total power dissipated in watts in the circuit shown here is 40 54 4 16 Three resistances P, Q, R each of 2 and an unknown resistance S form the four arms of a Wheatstone bridge circuit. When a resistance of 6 is connected in parallel to S the bridge gets balanced. What is the value of S? 3 6 1 2 See the electrical circuit shown in this figure. Which of the following equations is a correct equation for it ? 1-(i 1+i 2)R+i 1r 1=0 1-(i 1+i 2)R-i 1r 1=0 2-i 1r 2- 1-i 1r 1=0 - 2-(i 1+i 2)R+i 2r 2=0 The resistances of the four arms P , Q , R and S in a Wheatstone's bridge are 10 ohm, 30 ohm, 30 ohm and 90 ohm, respectively. The e.m.f. and internal resistance of the cell are 7 volt and 5 ohm respectively. If the galvanometer resistance is 50 ohm, the current drawn from the cell will be 1.0 A 0.2 A 0.1 A 2.0 A In the electrical circuit shown in the figure, the current i through the side AB is 6 25 A 10 33 A 1 5 A 10 63 A Two resistors of resistances R 1 and R 2 ( R 1 < R 2 ) are connected in parallel. The equivalent resistance R is: R < R 1 R > R 2 R 1 < R < R 2 R = (R 1 + R 2)/2 A set of 'n' equal resistors, of value 'R' each, are connected in series to a battery of emf 'E' and internal resistance 'R'. The current drawn is I. Now, the 'n' resistors are connected in parallel to the same battery. Then the current drawn from battery becomes 10 I. The value of 'n' is 20 11 10 9 Three resistors having resistances r 1 , r 2 and r 3 are connected as shown in the given circuit. The ratio i 3 i 1 of currents in terms of resistances used in the circuit is r 2 r 2+r 3 r 1 r 1+r 2 r 2 r 1+r 3 r 1 r 2+r 3 If the galvanometer G does not show any deflection in the circuit shown, the value of R is given by 200 Ω 50 Ω 100 Ω 400 Ω The magnitude and direction of the current in the following circuit is 0.2 A from B to A through E 0.5 A from A to B through E 5 9 A from A to B through E 1.5 A from B to A through E The current passing through the battery in the given circuit, is: 1.5 A 2.0 A 0.5 A 2.5 A A constant voltage of 50 V is maintained between the points A and B of the circuit shown in the figure. The current through the branch CD of the circuit is: 3.0 A 1.5 A 2.0 A 2.5 A A uniform metallic wire having resistance 4 is bent to form a square loop (ABCD) (see figure). A resistance of 2 is connected between points B and D and a battery of 2 V is connected across points A and C as shown in the figure. Now the value of current (I) is : 4 A 4.5 A 8 A 2 A Two resistances R 1 and R 2 are made of different materials. The temperature coefficient of resistance for R 1 is and for R 2 is - . The resistance of the series combination of R 1 and R 2 will not change with temperature if R 1/R 2 equals: / / ( + )/ /( + ) Two cities are 150 km apart. Electric power is sent from one city to another through copper wires. The fall of potential per km is 8 Volts and the average resistance per km is 0.5 . The power loss in the wire is: 19.2 kW 12.2 kW 19.2 J 12.2 W The temperature coefficient of resistance of a wire is 0.00125 per C . At 300 K its resistance is 1 . At what temperature will the resistance be 2 ? 1127 K 1100 K 1400 K 1127 C Which of the following materials is typically used to make standard resistance coils because its resistivity change with temperature is almost negligible? Manganin Copper Silicon Silver The resistance of a hollow cylinder of inner radius a , outer radius b , and length L , when current flows radially from inner to outer surface, is (resistivity is ): 2 L ( b a ) L (b 2-a 2) L 2 (b-a) 4 L (b-a) A fuse wire with a radius of 0.2 mm blows at a current of 5 A . For the same material, what current will cause a fuse wire with a radius of 0.4 mm to blow? 14.14 A 10 A 20 A 15 A A wire of resistance R is bent to form a circle. The resistance between two points on the circumference which subtend an angle at the center is: R (2 - ) 4 2 R 2 R(2 - ) 2 R 2 4 2 The temperature coefficient of resistance of a wire is 0.00125 per C . At 300 K its resistance is 1 . The resistance of the wire will be 2 at a temperature of: 1100 K 1127 K 800 C 1127 C If a copper wire is stretched such that its radius is reduced by 1 % , then the percentage increase in its resistance will be approximately: 4 % 2 % 1 % 8 % A wire of resistance 10 is shaped into a circle. The effective resistance between two points on the circumference which subtend an angle of 60 at the center is: 1.39 2.5 5 1.67 For the network shown in the figure the value of the current i is — 18V 5 5V 9 9V 35 5V 18 In the circuit shown, if a conducting wire is connected between points A and B, the current in this wire will- Flow from A to B Flow in the direction which will be decided by the value of V Be zero Flow from B to A Two cells, having the same e.m.f., are connected in series through an external resistance R. Cell have internal resistances r 1 and r 2 ( r 1 > r 2 ) respectively. When the circuit is closed, the potential difference across the first cell is zero. The value of R is:- r 1-r 2 r 1+r 2 2 r 1-r 2 2 r 1+r 2 Six similar bulbs are connected as shown in the figure with a DC source of emf E and zero internal resistance. The ratio of power consumption by the bulbs when (i) all are glowing and (ii) in the situation when two from section A and one from section B are glowing, will be : 2 : 1 4 : 9 9 : 4 1 : 2 A fuse wire should have: High resistivity and low melting point Low resistivity and high melting point High resistivity and high melting point Low resistivity and low melting point Choose the correct circuit which can achieve the bridge balance. Consider two circuits, (A) and (B), each having two resistors. One of them has a positive temperature coefficient of resistance, + , while the other one has a negative temperature coefficient, - , as shown in the figure. The current through these circuits are denoted by I A and I B . At initial temperature, the resistance of the two resistors is R 0 . As the temperature is increased, the correct option that describes the variation of current in these circuits is: I A remains constant while I B increases I A decreases while I B increases I A increases while I B decreases I A and I B remain constant The temperature coefficient of resistance of a semiconductor is: Negative Positive Zero Constant The color code of a carbon resistor is: Blue, Black, Yellow, Silver. What is its resistance? 600 10 % k 60 5 % k 600 5 % k 60 10 % k Three resistors 1 , 2 , and 3 are connected in parallel. The ratio of currents flowing through them is: 6:3:2 1:2:3 3:2:1 2:3:6 The ratio of the amounts of heat developed in two resistors of resistances R and 2R when connected in parallel to a constant voltage source is: 2:1 1:2 4:1 1:4 Which of the following is a non-ohmic conductor? Electrolyte Copper wire Manganin wire Constantan wire Which of the following remains constant when a steady current flows through a metallic conductor of non-uniform cross-section? Current Current density Drift velocity Electric field A uniform wire of resistance 10 and length 100 cm is cut into two pieces of lengths 40 cm and 60 cm . These pieces are then connected in parallel. The equivalent resistance of the parallel combination is: 2.4 4.0 6.0 10.0 The resistivity of a wire depends on its: Material Length Area of cross-section Shape The solids which have the negative temperature coefficient of resistance are: Semiconductors and insulators only Metals only Semiconductors only Insulators and metals The color code of a carbon resistor is: Yellow, Violet, Brown, Gold. The value of the resistance is: 470 5 % 47 10 % 4.7 5 % 4700 5 % A wire of resistance R is divided into n equal parts. These parts are then connected in parallel. The equivalent resistance of the combination is: R/n 2 R/n nR n 2 R Standard resistance coils are made of alloys like Manganin because they have: High resistivity and low temperature coefficient of resistance Low resistivity and high temperature coefficient of resistance Low resistivity and low temperature coefficient of resistance High resistivity and high temperature coefficient of resistance An electric bulb is rated 220 V and 100 W . When it is operated on 110 V , the power consumed will be: 25 W 50 W 75 W 100 W For which of the following substances, resistance decreases with the increase in temperature? Silicon Copper Silver Iron A carbon resistor has color bands: Brown, Black, Brown. What is its resistance value? 100 10 110 1 k Which of the following represents the vector form of Ohm's Law, where J is current density, is electrical conductivity, and E is electric field intensity? J = E J = E V = I R E = J The temperature coefficient of resistance for a wire is . If its resistance at 0 C is R 0 , then the resistance at t C is given by R t = R 0(1 + t) . This formula is valid when: The change in temperature is small. The material is a semiconductor. The temperature is measured in Kelvin only. The wire is made of a liquid metal. An electric bulb is rated 100 W, 200 V . If the line voltage drops to 150 V , the power consumed by the bulb is approximately: 56.25 W 75 W 25 W 44 W A carbon resistor is marked with rings of colors: Brown, Black, Green and Gold. The resistance value is: 1.0 M 5 % 100 k 10 % 1.0 k 5 % 10 M 5 % Which material is used for the manufacture of standard resistors because of its very low temperature coefficient of resistance and high resistivity? Manganin Copper Aluminum Iron The unit of electrical conductivity is: ohm -1 m -1 ohm m ohm -1 m ohm m -1 Two resistors R 1 and R 2 are connected in parallel to a constant voltage source. If R 1 > R 2 , then: More power is dissipated in R 2 More power is dissipated in R 1 Equal power is dissipated in both Current through R 1 is greater than R 2 A metallic conductor is heated. The product of its resistivity and conductivity: Remains constant Increases Decreases First increases then decreases The temperature coefficient of resistance of a material is 0.004 / C . If its resistance at 0 C is 10 , at what temperature will its resistance be 12 ? 50 C 25 C 100 C 80 C A carbon resistor is marked with rings of colors: Orange, Orange, Orange, and Silver. Its resistance and tolerance are: 33 k 10 % 330 10 % 3.3 k 5 % 33 k 5 % Which of the following remains constant for a non-ohmic conductor like a semiconductor diode? None of these The ratio V/I The slope of V-I graph The resistance In the circuit shown, if the potential at point A is 10 V , what is the potential at point B ? (Assume a 2 resistor between A and B with 3 A current flowing from A to B ) 4 V 16 V 7 V 13 V The unit of resistivity can be expressed as: V m A -1 V A -1 V m -1 A A m V -1 Two wires A and B are made of the same material. The length of A is twice that of B and the radius of A is half that of B . The ratio of their resistances R A/R B is: 8 4 2 16 Superconductors are materials that exhibit zero electrical resistance below a certain temperature called: Critical temperature Curie temperature Debye temperature Fermi temperature The resistance of a 100 W, 220 V bulb is R 1 and that of a 60 W, 220 V bulb is R 2 . Which of the following is true? R 1 < R 2 R 1 > R 2 R 1 = R 2 R 1 = 2R 2 A color-coded carbon resistor has bands in the order: Green, Blue, Red, and Silver. The resistance of the resistor is: 5600 10 % 560 5 % 5600 5 % 560 10 % Two conductors of the same material and same length have radii r 1 and r 2 . If they are connected in series, the ratio of the potential differences across them is: r 2 2 / r 1 2 r 1 2 / r 2 2 r 2 / r 1 r 1 / r 2 The unit of electrical resistivity is: ⋅m / m S/m ⋅m -2 A wire of resistance 4 is bent in the form of a circle. The effective resistance between two points on any diameter is: 1 2 4 0.5 A wire of length L and resistance R is stretched so that its length becomes 2L and area of cross-section is halved. The new resistivity will be: (Unchanged) 2 4 /2 Which of the following materials has a negative temperature coefficient of resistance? Germanium Copper Aluminum Iron Kirchhoff's first and second laws for electrical circuits are consequences of:- Conservation of energy Conservation of electric charge and energy respectively Conservation of electric charge Conservation of energy and electric charge respectively A student measures the terminal potential difference (V) of a cell (of emf and internal resistance r) as a function of the current (I) flowing through it. The slope and intercept of the graph between V and I, then respectively equal to : - and r and -r -r and r and - Three resistors 2 , 3 and 6 are connected in parallel. Their equivalent resistance is: 1 11 6 0.5 The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 is 0.2 0.5 0.8 1.0 A cell of emf E and internal resistance ‘r’ is connected to a variable external resistor ‘R’. The graph which gives the terminal voltage of cell ‘V’ with respect to R is A battery consists of a variable number 'n' of identical cells (having internal resistance 'r' each) which are connected in series. The terminals of the battery are short-circuited and the current I is measured. Which of the graphs shows the correct relationship between I and n? Which of the following acts as a circuit protection device? Fuse Conductor Inductor Switch The effective resistance of a parallel connection that consists of four wires of equal length, equal area of cross-section and same material is 0.25 . What will be the effective resistance if they are connected in series? 0.5 1 4 0.25 10 resistors, each of resistance R are connected in series to a battery of emf E and negligible internal resistance. Then those are connected in parallel to the same battery, the current is increased n times. The value of n is 10 100 1 1000 The terminal voltage of the battery, whose emf is 10 V and internal resistance 1 , when connected through an external resistance of 4 as shown in the figure is: 4 V 6 V 8 V 10 V A resistor is connected to a battery of 12 V emf and internal resistance 2 . If the current in the circuit is 0.6 A, the terminal voltage of the battery is: 12 V 1.2 V 10 V 10.8 V A filament bulb (500 W, 100 V ) is to be used in a 230 V main supply. When a resistance R is connected in series, it works perfectly and the bulb consumes 500 W . The value of R is: 26 13 230 46 An electric kettle has two heating coils. When one of the coils is connected to an AC source, the water in the kettle boils in 10 minutes . When the other coil is used, the water boils in 40 minutes . If both the coils are connected in parallel, the same amount of water will boil in: 8 minutes 25 minutes 50 minutes 4 minutes The temperature coefficient of resistance of a material is 0.004 / C . If the resistance at 0 C is 100 , its resistance at 100 C will be: 140 104 120 160 The resistance of a wire is 5 at 50 C and 6 at 100 C . The resistance of the wire at 0 C will be: 4 3 2 1 A set of n equal resistors, each of resistance R , when connected in series have an effective resistance R s and when connected in parallel, the effective resistance is R p . If R s - R p = 48 and n = 10 , the value of R is: 4.84 0.48 4.8 48 The resistance of a wire is R . It is stretched such that its radius becomes 1/n of its original value. The new resistance will be: n 4 R n 2 R n R n -4 R A carbon resistor has a resistance of 47 4.7 k . The color code sequence is: Yellow, Violet, Orange, Silver Yellow, Violet, Gold, Silver Violet, Yellow, Orange, Silver Green, Blue, Orange, Silver A wire of resistance 12 ohms/m is bent to form a complete circle of radius 10 cm . The resistance between its two diametrically opposite points, A and B , as shown in the figure is: 0.6 3 6 0.06 If the voltage across a bulb rated 220 V, 100 W drops by 2.5 % of its rated value, the percentage of the rated power that would decrease is: 5 % 2.5 % 10 % 1.25 % A copper wire is stretched to make it 0.1 % longer. The percentage change in its resistance is: 0.2 % 0.1 % 0.4 % 0.05 % Two bulbs are rated (25 W, 220 V ) and (100 W, 220 V ) . If they are connected in series across a 220 V source, which bulb will glow brighter? 25 W bulb 100 W bulb Both will glow with same brightness Neither will glow A wire of resistance 10 is bent to form an equilateral triangle. The effective resistance between any two vertices of the triangle is: 20 9 10 3 5 3 10 The resistance of a wire is R . If the length is increased by 0.1 % by stretching, the percentage increase in its resistance will be: 0.2 % 0.1 % 0.05 % 0.4 % A carbon resistor is marked with rings of colors: Yellow, Violet, Orange, and Silver. Its resistance is: 47 k 10 % 4.7 k 5 % 470 10 % 47 k 5 % Copper and silicon are cooled from 300 K to 60 K . The specific resistance: Decreases for copper but increases for silicon Increases for copper but decreases for silicon Decreases for both Increases for both If the length of a conductor is doubled and its cross-sectional area is halved, its conductance will: Become one-fourth Become four times Remain unchanged Double A heater coil is cut into two equal parts and only one part is used in the heater. The heat generated will now be: Doubled Halved One-fourth Four times A wire of resistance 16 is bent into the form of a square. The resistance between opposite corners is: 4 8 1 16 The temperature coefficient of resistance of a wire is 0.00125 per C . At 20 C , its resistance is 1 . The resistance of the wire will be 2 at: 820 C 800 C 700 C 600 C If the current I through a resistor R is increased by 100 % (temperature remains constant), the percentage increase in power dissipated is: 300 % 100 % 200 % 400 % Two wires of the same material have lengths in the ratio 1:2 and masses in the ratio 2:1 . The ratio of their resistances is: 1:8 1:4 4:1 8:1 Three identical bulbs are connected in series to a battery. They together dissipate power P . If now they are connected in parallel to the same battery, the power dissipated will be: 9P 3P P/3 P/9 The resistance of a conductor is 5 at 50 C and 7 at 100 C . The temperature coefficient of resistance of the material is: 0.0133 / C 0.0033 / C 0.008 / C 0.05 / C The temperature coefficient of resistance of a wire is 0.001 / C . At 300 K , its resistance is 1 . At what temperature will its resistance be 1.1 ? 400 K 310 K 427 K 100 K The unit of 'Conductance' is: Siemens Ohm-meter Siemens-meter Ohm A current of 3 A flows through the 2 resistor as shown in the circuit. The power dissipated in the 5 resistor is: 20 W 45 W 10 W 5 W The variation of resistivity ( ) with temperature (T) for Nichrome is best represented by which type of graph? A straight line with a non-zero intercept on the resistivity axis. A curve that is asymptotic to the temperature axis. An exponential increase starting from the origin. A parabola opening downwards. An electric bulb rated at 220 V, 40 W is connected to a 110 V supply. The power consumed by it is: 10 W 20 W 5 W 40 W If the copper wire is replaced by an aluminum wire of the same length and resistance, then the aluminum wire will be: Thicker than the copper wire Thinner than the copper wire Of the same thickness Denser than the copper wire Three identical resistors are connected in series and they dissipate 10 W of power. If they are connected in parallel to the same source, the power dissipated will be: 90 W 30 W 10/3 W 100 W A wire of resistance R is stretched such that its length increases by 10 % . The percentage increase in its resistance is: 21 % 10 % 20 % 11 % Two bulbs of 100 W and 40 W are connected in series across a 220 V line. The ratio of the power consumed by them ( P 100 /P 40 ) is: 2:5 5:2 1:1 4:100 Two wires of the same material have lengths in the ratio 2:3 and radii in the ratio 1:2 . The ratio of their resistances is: 8:3 2:3 4:3 1:3 A 5 A fuse wire can withstand a maximum power of 1 W . If the resistance of the fuse wire is doubled, the current it can withstand is: 3.54 A 2.5 A 10 A 5 A A copper wire of resistance R is cut into ten equal parts. Five parts are connected in series and the other five are connected in parallel. What is the ratio of the resistance of the series combination to the parallel combination? 25:1 5:1 10:1 100:1 A wire of resistance 4 is stretched to twice its original length. The resistance of the stretched wire would be: 16 8 2 4 The resistance of a conductor is 5 at 50 C and 6 at 100 C . The temperature coefficient of resistance is: 0.005 / C 0.01 / C 0.002 / C 0.02 / C A rectangular block has dimensions 1 cm 1 cm 10 cm . If the resistivity of the material is 3 10 -7 m , the maximum resistance between any two faces is: 3 10 -4 3 10 -6 3 10 -5 3 10 -3 An electric current is passed through a circuit containing two wires of the same material, connected in parallel. If the lengths and radii of the wires are in the ratio of 4:3 and 2:3 , then the ratio of the currents passing through the wires will be: 1:3 3:1 8:9 2:3 The resistance of a wire at 20 C is 20 and at 500 C is 60 . At what temperature will its resistance be 25 ? 80 C 70 C 60 C 50 C A wire of resistance 10 is stretched to three times its original length. It is then cut into three equal parts and these parts are connected in parallel. The equivalent resistance of the combination is: 10 3.33 30 90 A wire of resistance 12 is bent into a circle. The effective resistance between two points on the circumference that subtend an angle of 90 at the center is: 2.25 3.0 9.0 2.67 A carbon resistor is marked with rings of colors in the sequence: Gray, Red, Orange and Silver. The resistance value of the resistor is: 82 10 % k 8.2 10 % k 820 10 % 82 5 % k A wire of resistance 10 is stretched until its length is doubled. Then this new wire is again stretched until its length is doubled again. The final resistance of the wire is: 160 40 80 20 Three resistors of resistances 2 , 4 and 6 are connected in parallel to a constant voltage source. The ratio of the power dissipated in them respectively is: 6:3:2 2:4:6 3:2:1 1:1:1 Two wires of the same material and same length have cross-sectional areas in the ratio 1:4 . If they are connected in series across a battery, the ratio of the potential difference across them is: 4:1 1:4 1:1 16:1