Question
(a) A teacher demonstrates electromagnetic induction using the apparatus shown in Fig. 10.1.
The teacher pulls the magnet down until one end is inside the coil. The teacher then releases the magnet. The magnet moves up and down repeatedly. As it moves, one end of the magnet enters and leaves the coil.
Describe and explain the readings on the centre-zero millivoltmeter as the magnet enters and leaves the coil.
(b) Fig. 10.2 shows a system for transmitting electricity from a power station.
State the name of the device used in X and the name of the device used in Y.
X ……………………………………………………………………………………………………………………………..
Y ……………………………………………………………………………………………………………………………..
Answer/Explanation
Answer:
(a) any four from:
needle moves (one way) as N pole / magnet moves downward / into coil
as coil cuts across magnetic field (of magnet)
needle moves in opposite direction as N pole / magnet moves upward / out of coil
field is cut in opposite direction
needle at zero when spring at max extension
magnet is stationary so no cutting of field lines
(b) (device) X is a step-up transformer
(device) Y is a step-down transformer
Question
A student uses a coil and a magnet on a spring to generate an electromotive force (e.m.f.) that varies. He suspends the magnet above a coil as shown in Fig. 11.1.
(a) The student pulls the magnet through the coil to X and then releases it. The magnet moves up and down through the coil.
[1]
(b) State two ways of increasing the voltage induced in the coil.
1. ……………………………………………………………………………………………………………………………..
2. ……………………………………………………………………………………………………………………………..[2] [Total: 3]
Answer/Explanation
Ans: (a)top box ticked (alternating)
(b) any two from:increase strength of magnet/magnetic field
increase speed of magnet increase number of turns (of wire in coil)