EMF Internal Resistance & Cells — Practice Questions

Free NEET Physics multiple-choice questions on EMF Internal Resistance & Cells. Attempt each question and reveal the answer with a full explanation.

Which of the following instruments is preferred for the measurement of the internal resistance of a cell? Potentiometer Voltmeter of high resistance Ammeter of low resistance Wheatstone bridge For a cell of EMF E and internal resistance r , the maximum power delivered to an external resistance R occurs when: R = r R = r/2 R = 2r R = 0 When a battery of EMF E and internal resistance r is being charged by an external DC source of voltage V , the terminal potential difference across the battery is: V = E + Ir V = E - Ir V = E V = Ir - E A battery of EMF 10 V and internal resistance 3 is connected to a resistor. If the current in the circuit is 0.5 A , what is the resistance of the resistor? 17 20 15 23 The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 is: 0.5 0.05 5 1.0 The power dissipated in an external resistance R by a cell of EMF E and internal resistance r is maximum when: R = r R = r/2 R = 2r R A cell of EMF E and internal resistance r drives a current I through an external resistor R . The power delivered to R is maximum when R = r . What is the value of this maximum power? E 2 / 4r E 2 / r E 2 / 2r E 2 / 4R 2 If n identical cells, each of EMF E and internal resistance r , are connected in parallel, the total EMF and internal resistance of the combination are: E, r/n nE, nr E, nr nE, r/n A steady current of 1.5 amp flows through a copper voltameter for 10 minutes. If the electrochemical equivalent of copper is 30 10 -5 g coulomb -1 , the mass of copper deposited on the electrode will be 0.50 g 0.67 g 0.27 g 0.40 g. A galvanometer having a coil resistance of 60 shows full scale deflection when a current of 1.0 amp passes through it. It can be converted into an ammeter to read currents upto 5.0 amp by : Putting in parallel a resistance of 15 Putting in parallel a resistance of 240 Putting in series a resistance of 15 Putting in series a resistance of 240 In a potentiometer circuit a cell of EMF 1.5 V gives balance point at 36 cm length of wire. If another cell of EMF 2.5 V replaces the first cell, then at what length of the wire, the balance point occurs? 21.6 cm 64 cm 62 cm 60 cm Two cells of EMF E 1 and E 2 and internal resistances r 1 and r 2 are connected in series to an external resistance R . The current in the circuit is: (E 1 + E 2) / (R + r 1 + r 2) (E 1 - E 2) / (R + r 1 + r 2) (E 1 + E 2) / (r 1 + r 2) (E 1 - E 2) / R A cell having an emf E and internal resistance r is connected across a variable external resistance R . As the resistance R is increased, the plot of potential difference V across R is given by: A curve approaching E asymptotically. A straight line passing through the origin. A straight line with negative slope. A rectangular hyperbola. A battery consists of a variable number n of identical cells (each of emf E and internal resistance r ) connected in series. The terminals of the battery are short-circuited and the current I is measured. Which of the following graphs shows the correct relationship between I and n ? A horizontal straight line A straight line passing through the origin A hyperbola A parabola Two cells of emfs E 1 and E 2 and internal resistances r 1 and r 2 are connected in parallel. The equivalent emf of the combination is: (E 1 r 2 + E 2 r 1) / (r 1 + r 2) (E 1 r 1 + E 2 r 2) / (r 1 + r 2) E 1 + E 2 (E 1 + E 2) / 2 When a resistance of 2 is connected across the terminals of a cell, the current is 0.5 A . When the resistance is increased to 5 , the current is 0.25 A . The internal resistance of the cell is: 1.0 0.5 2.0 1.5 A cell of e.m.f. E and internal resistance r is connected to a variable external resistance R . The maximum power delivered by the cell to the external resistance R is: E 2 4r E 2 r E 2 2r 4E 2 r Two cells of emfs 1.5 V and 2.0 V having internal resistances 0.2 and 0.3 respectively are connected in parallel. The equivalent e.m.f. of the combination is: 1.7 V 3.5 V 0.5 V 1.3 V A current of 2 A flows through a 2 Ω resistor when connected across a battery. The same battery supplies a current of 0.5 A when connected across a 9 Ω resistor. The internal resistance of the battery is: 1/3 Ω 1/4 Ω 1/2 Ω 1 Ω In a mixed grouping of n identical cells (each of emf E and internal resistance r ) in m rows, each row containing n cells, the current through an external resistance R is maximum when: R = nr/m R = mr/n R = r/nm R = nmr Two non-ideal batteries are connected in parallel. Consider the following statements: (A) The equivalent EMF is smaller than either of the two EMFs. (B) The equivalent internal resistance is smaller than either of the two internal resistances. B is correct but A is wrong A is correct but B is wrong Both A and B are correct Both A and B are wrong In the series combination of n cells, each of EMF E and internal resistance r , the maximum current is drawn through an external resistance R when: R is much larger than nr R is much smaller than nr R = r/n R is independent of nr The internal resistance of a cell of e.m.f. 2 V is 0.1 . It is connected to a resistance of 3.9 . The voltage across the cell will be: 1.95 V 0.5 V 2 V 1.9 V The current in a circuit containing a battery of EMF E and internal resistance r is I . The plot of terminal voltage V vs current I is a straight line with: Negative slope -r and intercept E Positive slope r and intercept E Negative slope -E and intercept r Zero slope and intercept E Two batteries of EMF 4 V and 8 V and internal resistances 1 and 2 respectively are connected in parallel with their like terminals together. The equivalent EMF of the combination is: 5.33 V 6.0 V 12.0 V 4.0 V A storage battery is connected to a charger for charging. Which of the following is true about the direction of current and the terminal voltage V ? Current enters the positive terminal, V = E + Ir Current leaves the positive terminal, V = E - Ir Current enters the positive terminal, V = E - Ir Current leaves the positive terminal, V = E + Ir For a thermocouple, the neutral temperature is 270 C and the temperature of the cold junction is 20 C . The temperature of inversion is: 520 C 290 C 540 C 250 C Two batteries of EMF 12 V and 6 V and internal resistances 2 and 1 are connected in parallel with their opposite terminals together. The equivalent EMF of the combination is: 0 V 6 V 9 V 18 V A battery consists of n identical cells, each of emf E and internal resistance r , connected in series. If m cells are wrongly connected in the series combination, the net emf and net internal resistance of the battery are respectively: (n-2m)E and nr (n-m)E and nr (n-2m)E and (n-2m)r (n-m)E and (n-m)r Two identical batteries, each of emf E = 2 V and internal resistance r = 1 , are connected in parallel to an external resistance R = 0.5 . The current flowing through the external resistance R is: 2 A 1 A 4 A 0.5 A For a cell of emf E and internal resistance r , the variation of terminal voltage V with the current I drawn from it is a straight line. The slope of this line represents: -r +r The EMF E The external resistance R A cell of emf E is connected across an external resistance R . The potential difference across the terminals of the cell is found to be V . The internal resistance r of the cell is given by: ((E-V)/V)R ((V-E)/E)R ((E-V)/E)R (E-V)R A cell of EMF E and internal resistance r is connected to an external resistance R . The maximum power is delivered to R when R=r . Under this condition, the potential difference across the terminals of the cell is: E/2 E Zero 2E For a cell, the graph between the potential difference ( V ) across the terminals and the current ( I ) drawn from the cell is a straight line with a negative slope. The intercept on the V -axis represents: EMF of the cell Internal resistance Maximum current None of these A storage battery of EMF 12 V and internal resistance 1 is being charged by a 24 V DC supply. If a series resistor of 5 is used, the terminal voltage of the battery during charging is: 14 V 12 V 10 V 16 V The resistance of an ammeter is 13 and its scale is graduated for a current upto 100 amps. After an additional shunt has been connected to this ammeter it becomes possible to measure currents upto 750 amperes by this meter. The value of shunt-resistance is 2 0.2 2 k 20 The resistance in the two arms of the meter bridge are 5 and R , respectively. When the resistance R is shunted with an equal resistance, the new balance point is at 1.6 1 . The resistance 'R' is :- 10Ω 15Ω 20Ω 25Ω A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4 m long, When the resistance R, connected across the given cell, has values of. (i) infinity (ii) 9.5 The balancing lengths', on the potentiometer wire are found to be 3 m and 2.85 m, respectively. The value of internal resistance of the cell is 0.25 0.95 0.5 0.75 A potentiometer wire is 100 cm long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50 cm and 10 cm from the positive end of the wire in the two cases. The ratio of emf's is :- 5 : 1 5 : 4 3 : 4 3 : 2 In the circuits shown below, the readings of voltmeters and the ammeters will be V 2 > V 1 and i 1 > i 2 V 2 > V 1 and i 1 = i 2 V 1 = V 2 and i 1 > i 2 V 1 = V 2 and i 1 = i 2 A resistance wire connected in the left gap of a metre bridge balances a 10 resistance in the right gap at a point which divides the bridge wire in the ratio 3 : 2. If the length of the resistance wire is 1.5 m, then the length of 1 of the resistance wire is : 1.0 10 -1 m 1.5 10 -1 m 1.5 10 -2 m 1.0 10 -2 m A wheatstone bridge is used to determine the value of unknown resistance X by adjusting the variable resistance Y as shown in the figure. For the most precise measurement of X, the resistances P and Q Should be approximately equal and are small Should be very large and unequal Do not play any significant role Should be approximately equal to 2X Two cells, having the same e.m.f. are connected in series through an external resistance R . Cells 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 (r 1 + r 2)/2 r 1 r 2 / (r 1 + r 2) A storage battery of e.m.f. 8.0 V and internal resistance 0.5 is being charged by a 120 V DC supply using a series resistor of 15.5 . What is the terminal voltage of the battery during charging? 11.5 V 8.0 V 7.5 V 12.5 V A 12 V battery with internal resistance 0.5 is connected to a 11.5 resistor. The power dissipated in the resistor is: 11.5 W 12 W 12.5 W 10 W Two batteries of EMF 4 V and 8 V with internal resistances 1 and 2 are connected in parallel with opposite polarities. The equivalent EMF is: 0 V 12 V 6 V 4 V A wire of resistance R is connected to a cell of internal resistance r . The maximum power is delivered to the external resistance when: R = r R r R r R = 0 The internal resistance of a cell is the resistance of: The electrolyte and electrodes of the cell The vessel containing the electrolyte The external circuit connected to the cell The wire connecting the terminals A cell of EMF E and internal resistance r is short-circuited. The current through the cell is: E/r Zero Infinite E/R What is the maximum current that can be drawn from a battery of EMF E and internal resistance r ? E/r E/2r 2E/r Infinite