Complete an electric circuit consisting of a cell, an ammeter, a nichrome wire of length l [say, marked (1)] and a plug key, as shown in Fig. 12.5.
Figure 12.5 Electric circuit to study the factors on which the resistance of conducting wires depends
Now, plug the key. Note the current in the ammeter.
✅ Answer: Let's assume the current in the ammeter is 1 A.
Replace the nichrome wire by another nichrome wire of same thickness but twice the length, that is 2l [marked (2) in the Fig. 12.5]. Note the ammeter reading.
✅ Answer: Here, the ammeter reading decreases to one-half (0.5 A).
Now replace the wire by a thicker nichrome wire, of the same length l [marked (3)]. A thicker wire has a larger cross-sectional area. Again note down the current through the circuit.
✅ Answer: Here, reading is increased. If the cross-sectional area is doubled, the ammeter reading is also doubled (2 A).
Instead of taking a nichrome wire, connect a copper wire [marked (4) in Fig. 12.5] in the circuit. Let the wire be of the same length and same area of cross-section as that of the first nichrome wire [marked (1)]. Note the value of the current.
✅ Answer: Here, reading is changed.
Notice the difference in the current in all cases.
Does the current depend on the length of the conductor?
✅ Answer: Yes.
Does the current depend on the area of cross-section of the wire used?