Question

An AC adaptor for a telephone answering unit uses a transformer to reduce the line voltage of 238 V (rms) to a voltage 7.5 V. The rms current delivered to an answering system is 345 mA. If the primary (input) coil in the transformer in the adaptor has 260 turns, how many turns are there on the secondary (output) coil

Answer 1

8 turns

Step-by-step explanation:

Given that,

Primary voltage,
`V_P=238\ V`

Secondary voltage,
`V_S=7.5\ V`

No of coils in a primary coil,
`N_P=260`

We need to find the no of turns in the secondary coil. Let it is
`N_S`. For a transformer, the ratio is as follows :

`(N_S)/(N_P)=(V_S)/(V_P)\\\\N_S=(V_SN_P)/(V_P)\\\\N_S=(7.5* 260)/(238)\\\\N_S=8.19\ \text{turns}`

So, there are 8 turns in the secondary coil.