Transformer answers

More turns on the secondary means a step up transformer

Expect voltage to be higher and current to be lower on secondary

If 100 volts AC are applied at the primary what is the voltage at the secondary of this transformer

turns ratio is Np/Ns = 4/8 = 1/2

therefore the Vs = 2 x Vp = 2 x 100V = 200V

If 5 amp are input what current flows from the secondary?

Its a step up so voltage goes up and the current goes down by the same ratio as the turns

Therefore current out put Is = 2.5A
 

If 500 w are input how much power is output?

In an ideal transformer the power in is the power out

therefore the power out Ps = 500 w

this can be confirmed with answers already found

Is = 2.5A
Vs = 200V

P = IV  = 2.5 A x 200V = 500 w = .5Kw