
A carbon filament has a resistance of at . What must be the resistance of a copper filament placed in series with carbon so that the combination has the same resistance at all temperatures? Temperature coefficient of resistance of carbon and that of copper is .
Important Questions on Current Electricity



Five resistances, a battery and an ammeter are connected as shown in . Find, the ammeter reading.

Calculate the steady-state current through resistor in the circuit shown in Fig. The internal resistance of the battery is negligible and

As shown in Fig., a variable rheostat of is used to control the potential difference across a load.
If the resistance is , what is the potential difference across the load?

As shown in Fig., a variable rheostat of is used to control the potential difference across a load.
If the load is removed, what should be the resistance at to get between and ?

In the circuit shown in Fig., both the ammeter and the cell have negligible resistance. Three external resistors are identical. When the switch is opened, the ammeter reads . What will the ammeter read when the switch is closed?
