CAIE IGCSE Physics 4.2.2 Electric Current Topic Practice

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Covered syllabus points

4.2.2.1—Electric current is related to the4.2.2.2—Use of ammeters (analogue and digital)4.2.2.3—Electrical conduction in metals in4.2.2.4—Difference between direct current4.2.2.5—Electric current as charge passing a4.2.2.6—Conventional current is from positive

Question 1

[Maximum number: 1]

A circuit contains two fixed resistors and a light-dependent resistor (LDR). Fig. 8.1 shows that the power supply is a 9.0 V battery.

Fig. 8.1

Fig. 8.1

The current in the 450Ω450 \Omega resistor is 0.012 A .

State what is meant by electric current.

Question 2

[Maximum number: 1]

Fig. 10.1 shows an incomplete electrical circuit.

Fig. 10.1

Fig. 10.1

A student completes the circuit and measures the current in the 6.0Ω6.0 \Omega resistor.

On Fig. 10.1, draw an ammeter symbol in one gap and straight lines to indicate wires in the other gaps to show how the student should do this.

Question 3

[Maximum number: 5]

Fig. 6.1 shows an isolated metal sphere suspended by an insulating thread from the ceiling.

Fig. 6.1

Fig. 6.1

The sphere is negatively charged.

Question (a)

(a)

The magnitude of the charge on the sphere is 3.5×10−10C3.5 \times 10^{-10} \mathrm{C}.

An earthed metal wire is touched against the surface of the sphere and the sphere is discharged.

[ 5 ]

Question (i)

(i)

State what happens in the wire as the sphere is discharged.

[ 2 ]

Question (ii)

(ii)

It takes a time of 0.14 ns for the sphere to discharge completely.

Calculate the average current in the earthed wire as the sphere discharges.

[ 3 ]
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