Ch.3 Electricity Form 5

Diagram 1 shows a candle flame is placed in an electric field.The observation on the shape of the flame is due to

• the number of negative ions is greater than the number of positive ions.

• the number of positive ions is greater than the number of negative ions.

• negative ions is heavier than positive ions.

• positive ions is heavier than negative ions

Diagram 2 shows a lightning phenomenon. The potential difference between two parts of a thundercloud is 108 V. During a lightning flash, 200 C of charges flow. Calculate the amount of currents flow in 2 seconds.

• 100 A

• 200 A

• 1 × 10¹⁰A

• 2 × 10¹⁰A

Diagram 3 shows a torchlight containing two dry cells, a switch and a lamp. Which of the following is the circuit diagram for the above torchlight?

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Diagram 4 shows wiring system for bulbs L₁,L₂,L₃ and L₄. Each bulb is labelled 12 V, 30 W. Power supply of 12 V is connected across XY

• 0.4 A

• 2.5 A

• 7.5 A

• 10.0 A

Which of the following combination of switches should be closed to make bulb S light up brighter?

• 1 and 2

• 1 and 3

• 2 and 3

• 1,2 and 3

Diagram 6 shows the rice cooker with a thicker wire cabel compared with the mobile phone.When the thickness of the wire increases, the resistance decreases. Why?

• The bigger cross-sectional area allows more electrons to flow through the wire per unit time

• The bigger circumferential area allows more electrons to flow through the wire per unit time.

• There are more electrons present in the wire.

• There are more protons present in the wire.

All bulbs in the circuits below are identical. Which circuit has the smallest effective resistance?

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Electromotive force is defined as

• the work done by an appliance in driving electrons around a circuit

• the work done by a source in driving a unit charge around a circuit

• the work done to drive a unit charge through a component

• the product of current and resistance

Diagram 12 shows a circuit. What is the electrical energy used by a lamp when the switch is on in 5 minutes if there is no internal resistance in the batteries of 12 V?

• 1.2 x 10² J

• 3.6 × 10² J

• 1.4 × 10³ J

• .2 × 10³ J

The following four electrical appliances are left switched on for different time. Which appliance uses the greatest amount of energy?

• A

• B

• C

• D