Ohm's law and figure of merit of a galvanometer — NEET & JEE Questions

Question 1 · difficulty L1 · recall

Ohm's law for an ohmic conductor at constant temperature is

• A. V=IR
• B. V=I/R
• C. V=R/I
• D. VI=R

Question 2 · difficulty L1 · understanding

A V-I graph for an ohmic resistor is

• A. a circle
• B. a straight line through the origin
• C. always horizontal
• D. an exponential decay

Question 3 · difficulty L2 · understanding

If a V-versus-I graph has slope 5 V/A, resistance is

• A. 0.2 Ω
• B. 25 Ω
• C. 5 Ω
• D. 5 A

Question 4 · difficulty L2 · application

The figure of merit k of a galvanometer is commonly defined as

• A. deflection per unit voltage only
• B. resistance per unit current
• C. voltage required per metre
• D. current required per unit scale division of deflection

Question 5 · difficulty L2 · understanding

The figure of merit of a galvanometer is defined as

• A. the deflection produced per unit current
• B. its resistance in ohms
• C. the current required to produce a deflection of one division on its scale
• D. the maximum current it can carry

Question 6 · difficulty L3 · application

If a galvanometer current of 20 μA produces 40 divisions, its figure of merit is

• A. 0.5 μA/division
• B. 2 μA/division
• C. 800 μA/division
• D. 20 μA/division

Question 7 · difficulty L3 · application

Why should resistor temperature be kept nearly constant when verifying Ohm's law?

• A. Voltage has no meaning at different temperature
• B. Resistance can change with temperature
• C. Current ceases to flow if warm
• D. Ohm's law requires zero resistance

Question 8 · difficulty L3 · application

A galvanometer of resistance 10 $\Omega$ is connected in series with a resistance box set to 4990 $\Omega$ and a cell of emf 2.0 V (negligible internal resistance). The deflection is 20 divisions. The figure of merit of the galvanometer is

• A. 4 x 10$^{-4}$ A div$^{-1}$
• B. 2 x 10$^{-4}$ A div$^{-1}$
• C. 5 x 10$^{4}$ A div$^{-1}$
• D. 2 x 10$^{-5}$ A div$^{-1}$

Question 9 · difficulty L3 · application

In an experiment to verify Ohm's law, a student records a current of 0.20 A when the voltmeter reads 1.0 V, and 0.40 A when it reads 2.0 V. Which conclusion and which circuit arrangement are correct?

• A. The resistance is 5.0 $\Omega$ and the wire obeys Ohm's law over this range; the ammeter was in series with the wire and the voltmeter in parallel with it
• B. The resistance is 0.20 $\Omega$; the ammeter was in parallel and the voltmeter in series
• C. The resistance is 5.0 $\Omega$; both meters were in series
• D. The resistance cannot be found without the length of the wire

Question 10 · difficulty L4 · analysis

A resistor carries 0.20 A at 3.0 V and 0.40 A at 6.0 V. These readings are consistent with resistance

• A. 7.5 Ω
• B. 30 Ω
• C. 15 Ω
• D. 1.5 Ω