Wheatstone Meter Bridge & Potentiometer — Practice Questions

Free NEET Physics multiple-choice questions on Wheatstone Meter Bridge & Potentiometer. Attempt each question and reveal the answer with a full explanation.

A potentiometer wire of length 4 m is connected across a 2 V battery. A cell of emf 1.08 V is balanced against a length l of the wire. The balancing length l is: 216 cm 200 cm 108 cm 250 cm In a potentiometer, the potential gradient of the wire is 2 mV/cm . A balance point is obtained for a cell at 400 cm . If the potential gradient is increased to 4 mV/cm , the new balance point will be at: 200 cm 800 cm 400 cm 100 cm If the length of a potentiometer wire is increased, then the accuracy of the potentiometer: Increases Decreases Remains same First increases then decreases In a potentiometer, a long wire is used to: Decrease the potential gradient and increase sensitivity Increase the potential gradient and increase sensitivity Decrease the potential gradient and decrease sensitivity Increase the resistance and current in the wire In a meter bridge, the balancing length is l = 25 cm from the left end. If the resistance in the left gap is 10 , the resistance in the right gap is: 30 40 20 10 Which of the following statements about a potentiometer is false? It can be used to measure the capacitance of a capacitor. It is used to compare the EMFs of two cells. It is used to measure the internal resistance of a cell. It measures EMF more accurately than a voltmeter because it draws no current at balance. If the length of a potentiometer wire is increased, keeping the voltage of the driver cell constant, the potential gradient will: Decrease Increase Remain the same Become zero In a potentiometer circuit, a cell of EMF 1.5 V gives a 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 will the balance point occur? 60 cm 64 cm 62 cm 21.6 cm The resistance of a potentiometer wire is r ohms. A cell of EMF E is connected across the wire. If a resistance R is connected in series with the wire, the potential gradient along the wire will be: (Er) / [(R+r)L] E / (R+r) EL / (R+r) (ER) / [(R+r)L] A potentiometer wire of length L and a resistance r are connected in series with a battery of e.m.f. E 0 and a resistance r 1 . An unknown e.m.f. E is balanced at a length l of the potentiometer wire. The e.m.f. E will be given by: E 0 rl / [ (r + r 1) L ] E 0 l / L E 0 r l / (r 1 L) E 0 r 1 l / (r L) 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 emfs is: 3:2 5:1 5:4 3:4 In the Wheatstone bridge shown, the galvanometer G shows zero deflection. If the battery is 10 V and has negligible internal resistance, find the value of X . 2 4 6 8 The current in the primary circuit of a potentiometer is 0.2 A . The specific resistance and area of cross-section of the potentiometer wire are 4 10 -7 m and 8 10 -7 m 2 respectively. The potential gradient will be: 0.1 V/m 0.2 V/m 1 V/m 0.5 V/m In a Wheatstone bridge, if the battery and galvanometer are interchanged, then the deflection in the galvanometer will: Not change Change in opposite direction Change in same direction Become zero In an experiment of potentiometer for measuring the internal resistance of primary cell, a balance point is obtained on a length l when the cell is in open circuit. Now a resistance of 10 is connected across the cell. If the balance point is now obtained at a distance l/2 from the same end, then the internal resistance of the cell is: 10 5 20 15 In a Wheatstone bridge, the four resistances are P=10 , Q=10 , R=10 and S=15 . What resistance should be connected in parallel with S to balance the bridge? 30 10 15 20 A potentiometer wire has a length of 10 m and a resistance of 20 . It is connected in series with a battery of e.m.f. 3 V and negligible internal resistance and a resistance of 10 . The potential gradient on the wire is: 0.2 V/m 0.1 V/m 0.3 V/m 0.02 V/m In a potentiometer experiment, the balancing length is l . If the current in the primary circuit is increased, the balancing length will: Decrease Increase Remain same Become zero Two cells of emfs E 1 and E 2 are connected in series. When they assist each other, the balancing length on a potentiometer is l 1 . When they oppose each other, the balancing length is l 2 . The ratio E 1/E 2 is: (l 1 + l 2) / (l 1 - l 2) (l 1 - l 2) / (l 1 + l 2) l 1 / l 2 l 2 / l 1 In a potentiometer experiment, the balancing length is 250 cm for a cell. When the cell is shunted by a resistance of 5 , the balancing length becomes 150 cm . The internal resistance of the cell is: 3.33 2.5 1.5 5 A 10 m long wire of resistance 20 is connected in series with a battery of EMF 3 V and a resistance of 10 . The potential gradient along the wire in V/m is: 0.2 0.3 0.1 1.2 In the Wheatstone bridge circuit, the bridge is balanced when the ratio of resistances is P/Q = R/S . If the positions of the battery and galvanometer are interchanged, the balance condition: Remains the same Changes to P/R = Q/S Changes to P/S = R/Q Becomes unstable A potentiometer is an accurate and versatile device to make electrical measurements of E.M.F. because the method involves: A condition of no current flow through the galvanometer A combination of cells, galvanometer and resistances Cells Potential gradients In a potentiometer experiment, the balancing length with a cell is 560 cm . When an external resistance of 10 is connected in parallel to the cell, the balancing length changes to 412 cm . The internal resistance of the cell is approximately: 3.6 2.4 1.5 5.2 A meter bridge is balanced with known resistance R in the left gap and unknown S in the right gap. The null point is at 40 cm . If R and S are interchanged, the null point will shift by: 20 cm 40 cm 60 cm 10 cm In a Wheatstone bridge, the bridge is most sensitive when: All four resistances are of the same order of magnitude Two resistances are very high and two are very low The galvanometer resistance is very high The battery voltage is very high In a meter bridge, the balancing length is l . If the radius of the bridge wire is doubled, the balancing length will: Remain the same Be doubled Be halved Be four times The resistance of a 10 m long potentiometer wire is 20 . It is connected in series with a 3 V battery and a 10 resistor. The potential gradient is: 0.2 V/m 0.3 V/m 0.1 V/m 2.0 V/m In a potentiometer experiment, the balancing length is L . When the battery in the primary circuit is replaced by one with double the EMF and half the internal resistance (but same potentiometer wire), the balancing length for the same unknown cell will: Decrease Increase Remain same Become zero In a potentiometer, the potential gradient is 0.2 V/m . A cell of EMF 1.1 V is balanced against a length of the wire. If the current in the primary circuit is halved, the new balancing length will be: 11 m 5.5 m 2.75 m 22 m The potential difference ( V A - V B ) between the points A and B in the given figure is: 9 V -3 V 3 V 6 V A potentiometer wire of length 100 cm has a resistance of 10 . It is connected in series with a resistance and a cell of EMF 2 V and negligible internal resistance. A source of EMF 10 mV is balanced against a length of 40 cm of the potentiometer wire. What is the value of the external resistance? 790 810 100 250 In a potentiometer experiment, the balancing length is 80 cm when a cell is in an open circuit and 60 cm when the cell is short-circuited through a resistance of 6 . The internal resistance of the cell is: 2 1.5 3 4 A 10 m long potentiometer wire carries a steady current. A standard cell of 1.018 V is balanced at 509 cm . The potential gradient of the wire is: 0.002 V/cm 0.02 V/cm 0.2 V/cm 2 V/cm The potential gradient of a potentiometer wire is k . If the current in the primary circuit is increased by 2 % , the new potential gradient will be: 1.02k 0.98k k 1.04k In a potentiometer experiment, two cells of emfs E 1 and E 2 are connected in series to support each other and then in opposition. The balancing lengths on the potentiometer wire are 6 m and 2 m respectively. The ratio E 1/E 2 is: 2:1 3:1 4:1 3:2 In a potentiometer circuit, the potential gradient of the wire is k . A cell of EMF E is balanced at a length l . If a resistance R is connected in parallel to the cell, the balance point shifts to l' . The internal resistance of the cell is given by: r = R ( l-l' l' ) r = R ( l'-l l ) r = R ( l l' ) r = R ( l' l ) Sensitivity of a potentiometer can be increased by: Decreasing the potential gradient Increasing the potential gradient Decreasing the length of the wire Increasing the current in the primary circuit A voltmeter of resistance 2000 reads 40 V when connected across a 100 V DC supply in series with a resistor R . The value of R is: 3000 1000 2000 5000 A potentiometer wire has length 4 m and resistance 8 . The resistance that must be connected in series with the wire and an accumulator of e.m.f. 2 V , so as to get a potential gradient 1 mV/cm on the wire is: 32 40 44 48 A potentiometer wire of length 100 cm has a resistance of 10 . It is connected in series with a resistance and a cell of emf 2 V and of negligible internal resistance. A source of emf 10 mV is balanced against a length of 40 cm of the potentiometer wire. What is the value of external resistance? 790 810 100 50 In a meter bridge, the balance point is found at a distance l 1 with resistances P and Q . When an unknown resistance X is connected in series with P , the balance point shifts to l 2 . The value of X is: Q( l 2 100-l 2 - l 1 100-l 1 ) Q( l 1 100-l 1 - l 2 100-l 2 ) Q( l 2 l 1 ) Q( 100-l 2 100-l 1 ) In a meter bridge experiment, the null point is obtained at 20 cm from one end when a resistance X is balanced against another resistance Y . If X < Y , then the null point for the combination of (X+Y) balanced against Y will be at: 54.5 cm 40 cm 60 cm 20 cm A potentiometer wire of length L and resistance 12r is connected to a battery of EMF E and internal resistance r . A cell of EMF E/4 and internal resistance r/2 will be balanced at a length: L/3 L/4 L/2 3L/4 The sensitivity of a potentiometer can be increased by: Increasing the length of the wire Decreasing the length of the wire Increasing the EMF of the primary cell Decreasing the resistance of the rheostat A network of four resistors of 6 , 12 , 15 and 20 are connected to form a Wheatstone bridge. To balance the bridge, what resistance should be connected in parallel to the 20 resistor? (Order: P=6, Q=12, R=15, S=20 ) 60 30 10 20 In a Wheatstone bridge, the resistance in the three arms are P, Q, and R and its fourth arm has a resistance S . The bridge is balanced. If P and Q are interchanged, the bridge becomes unbalanced. To balance the bridge again, the resistance R must be changed to R' . The value of R' is: Q 2 R / P 2 P 2 R / Q 2 PR / Q QR / P In a meter bridge experiment, the null point is obtained at 33.7 cm from one end. When a resistance of 12 is connected in parallel with the resistance in the right gap, the null point shifts to 51.9 cm . The original resistance in the right gap was: 13.5 6.8 2 15 In a meter bridge experiment, the null point is obtained at 20 cm from the left end. When the resistance in the left gap is increased by 10 , the null point shifts to 40 cm . The initial resistance in the left gap was: 6 10 15 20 In a meter bridge, the balance point is at 40 cm . If the resistance in the left gap is shunted by an equal resistance, the new balance point will be at: 25 cm 20 cm 50 cm 60 cm In a meter bridge, the copper strips are thick to: Minimize the resistance of the connections Minimize the heating effect Make the bridge more sensitive Increase the resistivity Sensitivity of a potentiometer can be increased by: Increasing the length of the potentiometer wire Increasing the EMF of the primary cell Decreasing the length of the potentiometer wire Increasing the resistance in the secondary circuit In a meter bridge experiment, the null point is obtained at l from the left end. If the two resistances in the gaps are interchanged, the new null point will be at: 100 - l l 50 - l 50 + l In an unbalanced Wheatstone bridge, the current flows through the galvanometer from higher potential to lower potential. If the potentials at the galvanometer terminals are V B and V D , current flows from B to D if: V B > V D V B < V D V B = V D The battery is reversed