Electric Circuits Summative

Two resistors of resistance 10 Ω and 20 Ω are connected in parallel to a cell.

The energy dissipated in the 10 Ω resistor in one second is Q. What is the energy dissipated in one second in the 20 Ω resistor?

• Q/4

• Q/2

• 4Q

• 2Q

An ideal ammeter is used to measure the current in a resistor. Which of the following gives the resistance of an ideal ammeter and the way it is connected to the resistor?

• Resistance = infinite, Connection = in parallel

• Resistance = infinite, Connection = in series

• Resistance = zero, Connection = in parallel

• Resistance = zero, Connection = in series

The circuit shows a resistor R connected in series with a 20 V battery and a resistor of resistance 10 Ω. The current is 1.0 A.

Which of the following is the resistance of R?

• 1.0 Ω

• 2.0 Ω

• 10 Ω

• 20 Ω

Resistors of resistance R, R and 3R are connected to a cell. The diagram shows three currents, I_x, I_y and I_z in the resistors. What is the correct relationship between the currents?

• I_{x =} I_y

• I_{y =} 3 I_z

• I_z = 3 I_x

• I_{x =} I_y + 3 I_z

A heating coil is connected to a 10 V battery. The power dissipated in the coil is 25 W. What is the resistance of the coil?

• 0.25 Ω

• 2.5 Ω

• 4.0 Ω

• 250 Ω

In a lightning flash a charge of 15 C flows in 0.5 m s. What is the average current?

• 33 μA

• 7.5 mA

• 30 A

• 30 kA

A filament lamp and a semiconducting diode have the voltage-current characteristics shown and are connected in parallel.

What is the resistance of the lamp and the resistance of the diode when the current in each device is 2.0 A?

• Lamp 1.0 Ω and Diode 0.25 Ω

• Lamp 1.0 Ω and Diode 0.50 Ω

• Lamp 0.50 Ω and Diode 0.25 Ω

• Lamp 0.50 Ω and Diode 0.50 Ω

Three resistors of resistance R are connected in parallel across a battery of potential difference V. What is the rate at which the battery supplies energy?

• $\frac{V^2}{3R}$

• $\frac{V^2}{9R}$

• $\frac{9V^2}{R}$

• $\frac{3V^2}{R}$

A current of 50.0 A flows through a cross-section of a wire. After six hours, what is the total number of all of the electrons which have passed through the cross section?

Charge of electron = 1.60 x 10^-19 C

• 1.08 x 10⁶ electrons

• 6.75 x 10²⁴ electrons

• 1.125 x 10²³ electrons

• 1.45 x 10¹⁶ electrons

The volt is equivalent to which combination of units?

• J C^-1

• C J^-1

• W C^-1

• C W^-1