P.3.5.1.4 Circuits

Three identical cells, each of emf 1.5 V and internal resistance 6.0 Ω, are connected to resistor R. The resistance of R is 6.0 Ω.

What is the current in R?

• 0.19 A

• 0.25 A

• 0.56 A

• 0.75 A

A power of 100 kW at a potential difference of 10 kV is transmitted to a load resistor through cables of total resistance 5.0 Ω.

What is the power loss in the cables?

• 50 W

• 0.5 kW

• 100 kW

• 20 MW

Resistors X and Y are connected in series with a 6.0 V battery of negligible internal resistance.

X has resistance R and Y has resistance R/2

A voltmeter of resistance R is connected across Y.

What is the reading on the voltmeter?

• 0.0 V

• 1.5 V

• 3.0 V

• 4.5 V

In the circuit shown, a potential difference of 3.0 V is applied across XY.

What is the current in the 5 Ω resistor?

• 0.38 A

• 0.60 A

• 0.75 A

• 2.7 A

The diagram shows part of a circuit and the currents in the circuit.

What is the potential difference between point P and earth?

• 60 V

• 100 V

• 120 V

• 140 V

A voltmeter has a resistance of 4.0 kΩ and reads 1.0 V for every scale division on the meter.

A power supply of emf 20 V and negligible internal resistance is connected across this voltmeter and a resistor in series. The voltmeter reads two divisions.

What is the value of the resistor?

• 44 kΩ

• 36 kΩ

• 4.4 kΩ

• 3.6 kΩ

Two cylindrical wires P and Q are of equal length and made of the same material.The diameter of P is greater than that of Q. P and Q are connected in series and the ends of this arrangement are connected to a power supply.

Which two quantities are the same for P and Q?

• potential difference across wire

  resistivity

• resistivity

  current

• current

  resistance

• resistance

  potential difference across wire

In the circuit below, the initial voltmeter reading is zero.

The temperature of the negative temperature coefficient thermistor T is then increased.

Which change to the circuit could restore the voltmeter reading to zero?

• Decreasing the resistance of R.

• Increasing the resistance of R.

• Decreasing the resistance of P.

• Increasing the resistance of Q.

An electric motor lifts a load of weight W through a vertical height h in time t.The potential difference across the motor is V and the current through it is I.

What is the efficiency of the motor?

• 
• 
• 
• 

Which graph shows how power dissipated P varies with current I in a component that obeys Ohm’s law?

• A

• B

• C

• D