TYS 5105 C11 (D.C. Circuits)

Which circuit is used to vary the brightness of a lamp?

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Answer explanation

In the circuit shown, the switches S1 and S2 may be open (off) or closed (on).

Which row shows the voltmeter reading when the switches are in the positions given in the table?

• S1: open,

  S2: open,

  voltmeter reading/V:

  12

• S1: closed,

  S2: closed,

  voltmeter reading/V:

  12

• S1: open,

  S2: closed,

  voltmeter reading/V:

  0

• S1: closed,

  S2: open,

  voltmeter reading/V:

  12

Answer explanation

Three 240V lamps, of different power ratings, are connected as shown. In which circuit are all three lamps lit at their normal brightness?

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Answer explanation

Four lamps and four switches are connected to a power supply as shown in the circuit diagram. When all the switches are closed, all the lamps are lit. When one of the switches is then opened, only one lamp goes out. Which switch is opened?

• A

• B

• C

• D

Answer explanation

In the circuit shown, the reading on ammeter 1 is 2A.

What is the reading on ammeter 2?

• 0 A

• 1 A

• 2 A

• 4 A

Answer explanation

A circuit containing three resistors with resistances, X, Y and Z, is set up.

Which formula can be used to find the total effective resistance, R_total, of the three resistors?

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Answer explanation

The circuit shown is set up.

Which statement is correct?

• voltage across lamp 2 is higher than the voltage across lamp 1

• voltage across lamp 1 is higher than the voltage across lamp 2

• voltage of battery = voltage across lamp 1 + voltage across lamp 2

• voltage of battery = voltage across lamp 1 = voltage across lamp 2

Answer explanation

A battery is connected to a switch and a motor. The speed of the motor depends on the potential difference across the motor.

Which component is connected in series with the motor so that the speed of the motor can be varied?

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Answer explanation

The diagram shows a circuit.

Which pair of statements shows the relationships between the readings on the meters?

• A 1 = A2 = A3 + A4 and V1 = V2 = V3 = V4

• A 1 = A 2 = A 3 + A4 and V1 = V2 + V3 + V4

• A 1 = A2 = A3 = A4 and V1 = V2 = V3 = V4

• A 1 = A 2 = A3 = A4 and V1 = V2 + V3 + V4

Answer explanation

The diagram shows a circuit containing three lamps connected in parallel. The switch is closed .

How is the potential difference (p.d.) across each of the working lamps, M and N, affected when one lamp breaks, as shown?

• p.d. across M: decreases,

  p.d. across N:

  decreases

• p.d. across M: increases,

  p.d. across N:

  decreases

• p.d. across M: increases,

  p.d. across N:

  increases

• p.d. across M: unchanged,

  p.d. across N:

  unchanged

Answer explanation