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Question 1

HLPaper 1

A capacitor is charged by a constant current of 2.5 μA for 100 s. As a result the potential difference across the capacitor increases by 5.0 V.

What is the capacitance of the capacitor?

Question 2

HLPaper 1

A conducting square coil is placed in a region where there is a uniform magnetic field.The magnetic field is directed into the page. There is a clockwise current in the coil. What is a correct force that acts on a side of the coil? Question

Question 3

HLPaper 1

The current I flowing in loop A in a clockwise direction is increasing so as to induce a current both in loops B and C. All three loops are on the same plane.

M18/4/PHYSI/HPM/ENG/TZ2/33_01

What is the direction of the induced currents in loop B and loop C?

	Loop B	Loop C
A.	clockwise	clockwise
B.	clockwise	anti-clockwise
C.	anti-clockwise	clockwise
D.	anti-clockwise	anti-clockwise

Question 4

HLPaper 1

The input to a diode bridge rectification circuit is sinusoidal with a time period of 20 ms. Which graph shows the variation with time $t$ of the output voltage $V_{out}$ between X and Y?

Question 5

HLPaper 1

The graph shows the variation of an alternating current with time in a $4.0\ \Omega$ resistor.

Graph

What is the average power dissipated in the resistor?

Question 6

HLPaper 2

The diagram shows a sketch of an ideal step-down transformer. The number of turns in the primary coil is 1800 and that in the secondary coil is 90.

1.

State Faraday's law of induction.

[2]

2.

Explain, using Faraday’s law of induction, how the transformer steps down the voltage.

[4]

3.

The input voltage is $240$ V. Calculate the output voltage.

[2]

4.

Outline how energy losses are reduced in the core of a practical transformer.

[2]

5.

Step-up transformers are used in power stations to increase the voltage at which the electricity is transmitted. Explain why this is done.

[2]

Question 7

HLPaper 2

Three identical light bulbs, X, Y and Z, each of resistance 4.0 Ω are connected to a cell of emf 12 V. The cell has negligible internal resistance.

When fully charged the space between the plates of the capacitor is filled with a dielectric with double the permittivity of a vacuum.

1.

The switch S is initially open. Calculate the total power dissipated in the circuit.

[2]

2.

The switch is now closed. State, without calculation, why the current in the cell will increase.

[1]

3.

The switch is now closed. Deduce the ratio $\frac{{\text{{power dissipated in Y with S open}}}}{{\text{{power dissipated in Y with S closed}}}}$ .

[2]

4.

The cell is used to charge a parallel-plate capacitor in a vacuum. The fully charged capacitor is then connected to an ideal voltmeter.

The capacitance of the capacitor is $6.0 \mu F$ and the reading of the voltmeter is $12V$ .

Calculate the energy stored in the capacitor.

[1]

5.

Calculate the change in the energy stored in the capacitor.

[3]

6.

Suggest, in terms of conservation of energy, the cause for the above change.

[1]

Question 8

HLPaper 1

The graph shows the variation of the peak output power P with time of an alternating current (ac) generator.

graph1

Which graph shows the variation of the peak output power with time when the frequency of rotation is decreased?

graph2

Question 9

HLPaper 1

Why are high voltages and low currents used when electricity is transmitted over long distances?

Question 10

HLPaper 1

An alternating supply is connected to a diode bridge rectification circuit.

The conventional current in the load resistor

Topic 11 - Induction, Alternating Currents, & Capacitance

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