Question

To verify Ohm's law, a student is provided with a test resistor R_(T), a high resistance R_(1) . a small resistance R_(2), two identical galvometers G_(1) and G_(2) and voltage source V. The correct circuit to carry out the experiment is.

Answer 1

The correct circuit to carry out the experiment is resistor R_(T) in series with ammeter and a voltmeter ,connected in parallel to the R_(T)  connected in series with a voltage source.

• Galvanometer can be converted to an ammeter . This is done by connecting a  small resistance known as shunt resistance, R_(2) parallel to it.
• This can be connected to the resistor in series to measure the current through the circuit.
• Galvanometer can be converted to voltmeter also. This is done by connecting a high load , R_(1) in series with the galvanometer.
• This system can be connected in parallel across the resistance, to measure the voltage drop across the resistance.
• If Vo is the voltage drop measured by the voltmeter and I is the current detected by the ammeter, then,

By Ohm's Law

• Vo  is proportional to I
• Vo = IR in this circuit.

Here Vo will be equal to V as V is the only source and R is the only resistor.

Effect of other resistors will be negligible.