Transformers

Question 1

What is a transformer?

Answer 1

An electrical device that is either used to increase the voltage from a supply or decrease the voltage

Question 2

What principle does it work on

Answer 2

Mutual induction And uses only alternating current

Question 3

What is mutual induction

Answer 3

The effect caused when one coil carrying a current (primary) induces an emf (electromotive force) in a neighboring coil (secondary)

Question 4

What happens since the current is varying (a.c)

Answer 4

It increases from zero to maximum then back to zero and then changes direction every half cycle, the magnetic field/ magnetic flux varies as well. The field lines spread across the secondary coil as the current increases and then retracts as the current decreases. This causes the cutting of the field lines by the secondary coil, causing an emf to be induced.

Question 5

step down transformer

Answer 5

Np > Ns
Vp > Vs

Question 6

of turns of coil is proportional to

Answer 6

induced e.m.f Np/Ns = Vp/Vs

Question 7

step up transformer

Answer 7

Np<Ns
Vp<Vs

Question 8

IpVp=

Answer 8

IsVs (Pout= Pin)

Question 9

Ideal transformer equation

Answer 9

Np Vp Is
—– = ——- = ——-
Ns Vs Ip

Question 10

When power is transmitted at high voltage

Answer 10

Current will be very small

Question 11

P=

Answer 11

IV

Question 12

When power is constant

Answer 12

P= I^2R