Electric Current in Conductors Physics - Electric Current in Conductors

Can the potential difference across a battery be greater than its emf?

An electron gun emits 2.0 × 10¹⁶ electrons per second. What electric current does this correspond to?

A parallel-plate capacitor is filled with a dielectric material of resistivity ρ and dielectric constant K. The capacitor is charged and disconnected from the charging source. The capacitor is slowly discharged through the dielectric. Show that the time constant of the discharge is independent of all geometrical parameters like the plate area or separation between the plates. Find this time constant.

A bulb is made using two filaments. A switch selects whether the filaments are used individually or in parallel. When used with a 15V battery, the bulb can be operated at 5W, 10W or 15W. What should be the resistances of the filaments?

In an electrolyte, the positive ions move from left to right and the negative ions from right to left. Is there a net current? If yes, in what direction?

How many time constants will elapse before the current in a charging RC circuit drops to half of its initial value? Answer the same question for a discharging RC circuit.

Find the charge on the capacitor shown in figure.

Would you prefer a voltmeter or a potentiometer to measure the emf of a battery?

Is work done by a battery always equal to the thermal energy developed in electrical circuit? What happens if a capacitor is connected in the circuit?

The thermal energy developed in a current-carrying resistor is given by U = i² Rt and also by U = Vit. Should we say that U is proportional to i² or i?

One of your friends argues that he has read in the previous chapters that there can be no electric field inside a conductor. And hence there can be no current through it. What is the fallacy of this argument?

Sometimes it is said that "heat is developed" in a resistance when there is an electric current in it. Recall that heat is defined as the energy being transferred due to temperature difference. Is the statement in quotes technically correct?

A current passes through a wire of non-uniform cross-section. Which of the following quantities are independent of the cross-section?

1. The charge crossing in a given time interval.
2. Drift speed.
3. Current density.
4. Free-electron density.

A resistor of resistance R is connected to an ideal battery. If the value of R is decreased, the power dissipated in the resistor will:

1. Increase.
2. Decrease.
3. Remain unchanged.

Two non-ideal batteries are connected in parallel. Consider the following statements:

1. The equivalent emf is smaller than either of the two emfs.
2. The equivalent internal resistance is smaller than either of the two internal resistances.

1. Both A and B are correct.
2. A is correct but B is wrong.
3. B is correct but A is wrong.
4. Both A and B are wrong.

Identify the correct options:

1. An ammeter should have small resistance.
2. An ammeter should have large resistance.
3. A voltmeter should have small resistance.
4. A voltmeter should have large resistance.

Find the potential difference between the points A and B and between the points B and C of the figure. in steady state.

How many time constants will elapse before the energy stored in the capacitor reaches half of its equilibrium value in a charging RC circuit?

The amount of charge that passes in time t through a cross-section of a wire is,
Q(t) = At² + Bt + C.

1. Write the dimensional formulae for A, B and C.
2. If the numerical values of A, B and C are 5, 3 and 1, respectively, in S.I units, find the value of the current at t = 5s.