P.3.5.1.5 Potential divider

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 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.

The figure shows a light dependent resistor (LDR) and fixed resistor R connected in series across a cell. The internal resistance of the cell is negligible.

Which row shows how the readings on the ammeter and the voltmeter change when the light intensity incident on the LDR is increased?

• Ammeter reading: decreases

  Voltmeter reading: increases

• Ammeter reading: decreases

  Voltmeter reading: decreases

• Ammeter reading: increases

  Voltmeter reading: increases

• Ammeter reading: increases

  Voltmeter reading: decreases

The circuit shown is used to supply a variable potential difference (pd) to another circuit.

Which graph shows how the pd supplied V varies as the moving contact C is moved from position P to position Q?

• 
• 
• 
• 

In this resistor network, the emf of the supply is 12 V and it has negligible internal resistance.

What is the reading on a voltmeter connected between points X and Y?

• 0 V

• 1 V

• 3 V

• 4 V

In the circuit shown below, each of the resistors has the same resistance.

A voltmeter with very high resistance is connected between two points in the circuit.

Between which two points of connection would the voltmeter read zero?

• Q and U

• P and T

• Q and W

• S and U

In the circuit shown in the diagram the cell has negligible internal resistance.

What happens to the reading of both meters when the resistance of R is decreased?

• Reading of ammeter: increases

  Reading of voltmeter: increases

• Reading of ammeter: increases

  Reading of voltmeter: decreases

• Reading of ammeter: decreases

  Reading of voltmeter: increases

• Reading of ammeter: unchanged

  Reading of voltmeter: decreases

A potential divider circuit consists of a battery connected across a thermistor and variable resistor in series.

Which of the following causes the potential difference (pd) across the thermistor to increase?

• increasing the temperature of the thermistor

• increasing the resistance of the variable resistor

• reducing the emf of the battery

• adding a resistor across the variable resistor

The diagram shows two wires, P and Q, of equal length, joined in series with a cell. A voltmeter is connected between the end of Q and a point X on the wires. The p.d. across the cell is V. Wire Q has twice the area of cross-section and twice the resistivity of wire P. The variation of the voltmeter reading as the point X is moved along the wires is best shown by

• A

• B

• C

• D