Unit 1 Physics January 2009

Please choose one of the following options for each question:

1. A child’s toy is operated by a small motor. The potential difference across the motor is 6.0 V and the current in it is 0.20 A. The energy used by the motor in 120 s is

2. Which one of the following does not apply to sound waves?

3. Two coherent sources emit waves of wavelength λ in phase. At a point where the two waves meet they have a phase difference of 90° ( 2 radians). Which of the following could be the path difference at this point?

4. The four diagrams show waves of different wavelengths approaching slits of different widths

In which diagram will the diffraction be the greatest?

5. The heating element for an electric fire is made from a wire of resistance R. It is replaced with a wire of the same material which has the same length but is twice the diameter. The resistance of this second wire is

6. The diagram shows a resistor network.

The total resistance between points X and Y is

7. The speed of sound in steel is 6000 m s–1. The wavelength of an ultrasound wave of frequency 50 kHz travelling through a steel girder is

8. Which one of the following graphs correctly shows the relationship between potential difference (V) and current (I) for a filament lamp?

9. Light travels into a semicircular glass block as shown in the diagram. The ray of light reaches the straight edge of the block at an angle of incidence i.
The critical angle for glass is c.

Which one of the following statements is true for light at the straight edge?

10. When a fire engine moves away from an observer, the pitch of the siren heard by the observer decreases. This is because