Question 1

A signal that repeats periodically is displayed on the screen of a cathode-ray oscilloscope.

The screen has 1cm squares and the time base is set at 2.00 ms cm–1.

What is the frequency of this periodic signal?

  A  

50 Hz

  B  

100 Hz

  C  

125 Hz

  D  

200 Hz

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Question 2

Mains electricity is rated 230 V in the UK.

Which is correct?

  A  

the mean voltage is 163 V


  B  

the peak voltage is 230 V


  C  

the root mean square voltage is 325 V

  D  

the peak-to-peak voltage is 650 V

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Question 3

A coil with 20 circular turns each of diameter 60 mm is placed in a uniform magnetic field of flux density 90 mT.

Initially the plane of the coil is perpendicular to the magnetic field lines as shown in Figure X.

The coil is rotated about a vertical axis by 90° in a time of 0.20 s so that its plane

becomes parallel to the field lines as shown in Figure Y.

Assume that the rate of change of flux linkage remains constant.

What is the emf induced in the coil?

  A  

zero

  B  

1.3 mV

  C  

25 mV

  D  

100 mV

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Question 4

An alternating emf is induced in a coil rotating in a magnetic field.

What is the phase difference between the magnetic flux linkage through the coil and the emf?

0
3π​ rad
2π​ rad
π rad

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Question 5

A coil with three turns of wire is used in an experiment.

The graph shows the variation of magnetic flux linkage with time t for this coil.

What is the e.m.f. induced across the ends of the coil?

  A  

0 V

  B  

0.20 V

  C  

0.40 V

  D  

1.2 V

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Question 6

A coil with 500 turns is placed in a uniform magnetic field.

The average cross-sectional area of the coil is 3.0 × 10–4 m2.

The magnetic flux through the plane of the coil is reduced from 1.8 × 10–4 Wb to zero in a time t.

The average electromotive force (e.m.f.) induced across the ends of the coil is 0.75 V.

What is the value of t ?

  A  

3.6 × 10–5 s

  B  

2.4 × 10–4 s

  C  

0.12 s

  D  

8.3s

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Question 7

A sound wave is displayed on the screen of a cathode-ray oscilloscope, as shown.

The time-base setting is 0.50ms per division.

What is the frequency of the sound wave?

  A  

250 Hz

  B  

500 Hz

  C  

670 Hz

  D  

1,300 Hz

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Question 8

A student uses a cathode-ray oscilloscope (c.r.o.) to measure the period of a signal. She sets the time-base of the c.r.o. to 5 ms cm–1 and observes the trace illustrated below. The trace has a length of 10.0 cm.

What is the period of the signal?

  A  

7.1 × 10–6 s

  B  

1.4 × 10–5 s

  C  

7.1 × 10–3 s

  D  

1.4 × 10–2 s

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Question 9

A vertical conducting rod of length l is moved at a constant velocity v through a uniform horizontal magnetic field of flux density B.

Which of the rows gives a correct expression for the induced emf between the ends of the rod for the stated direction of the motion of the rod?

  A  
  B  
  C  
  D  

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Question 10

Three identical magnets P, Q and R are released simultaneously from rest and fall to the ground from the same height.

P falls directly to the ground.

Q falls through the centre of a thick horizontal conducting ring.

R falls through a similar ring that has a gap cut into it.

In which order do the magnets reach the ground?

  A  

P and R arrive together, followed by Q

  B  

P and Q arrive together, followed by R

  C  

P arrives first, followed by Q which is followed by R

  D  

all three magnets arrive simultaneously

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