Question

1. 4 pts each

   An ideal transformer within a phone charger takes 120 V from the wall and converts it into 5 V to the phone. The number of primary turns must be ? times more than the number of secondary turns .

   (Round your answer to the nearest whole number, do not put any decimals - so for example 1 and that's it.)

   If the phone can handle at most 2.4 A, then the current from the wall must be    ? less than  mA.

   (Notice that the required units are in milli-amperes, so convert properly. Round your answer to the nearest whole number, do not put any decimals - so for example 1 and that's it.)

Answer 1

as according to transformer equation,

Ns/Np = Vs/Vp

where N is the numbt of turns in the coil in primary (Np) and secondary coil(Ns). and Vs and Vp are the voltages of secondary and primary coil respectively.

using knwon values,

Ns/Np = 5/120

Np = 24 Ns

Number of turns in primary coil is 24 times than the secondary coil.

> Now for second part the current from the wall must be less than,

as the phone can bear only upto 2.4 A so,

1 A = 10³ mA

then 2.4 A = 2400 mA

Thus the current must be less than 2400 mA.