1.1. A student is provided with apparatus shown in Figure 1a. 

Figure 1a

A coil of wire is connected to a signal generator and the search coil is connected to an oscilloscope. When a sinusoidal alternating current is passed through the coil an alternating emf is induced in the search coil. 

An emf is induced in a coil of wire displayed on an oscilloscope with 8 vertical and 10 horizontal divisions as shown in Figure 1b.

Figure 1b

Draw the trace of the oscilloscope on Figure 1b if the frequency of the emf in the coil is 2500 Hz and the time-base setting is 0.2 ms cm^–1.

1.2. The student clamps the rectangular frame so that it remains in a vertical plane. Without changing the position of the search coil she rotates the circular frame about a vertical axis so that it is turned through an angle, as shown in Figure 2a. 

Figure 2a

She turns off the time−base on the oscilloscope so that a vertical line is displayed on the screen. The y−voltage gain is at 10 mV cm⁻¹ and she records the length L of the vertical line and the angle θ through which the circular frame has been rotated. 

The trace on the oscilloscope appears as shown in Figure 2b. 

Figure 2b

Describe two adjustments the student should make to the trace to reduce the uncertainty in L. 

You should refer to specific controls on the oscilloscope. You may use Figure 2a to illustrate your answer.

1.3. The student adjusts the signal generator so that the frequency of the emf in the circular coil is tripled. 

State and explain any changes she should make to the settings of the oscilloscope in part (b) so that she can repeat the experiment.