K.C.S.E Physics Q & A - MODEL 2001PP2QN02

K.C.S.E Physics Q & A - MODEL 2001PP2QN02

​ a) Fig 1 (a) shows the circuit of a simple telephone receiver. When the telephone is lifted, a steady current flows through the solenoids. When a person speaks into the microphone on the other side, a varying current flows. These two currents are shown in fig. 1(b).

​i) State the reason why solenoids are wounds in opposite directions around the soft-iron core pieces as shown.
ii) Explain how the speech current from the microphone is converted into sound in the receiver.
iii) State and explain the effect of replacing the soft iron core pieces with steel core pieces.
​b) A step down transformer has 400 turns in the primary coil and 20 turns in the secondary coil A 50 ohms resister is connected to the secondary output. If the r.m.s (root-mean-square) value of the primary voltage is 240; determine the peak value of the current in the in the secondary circuit.

answers