If the primary coil is
connected to an ac source, the primary and secondary voltages are
related by
V
NN
V
s
s
p
p
=




and the currents are related by
I
N
N
I
s
p
s
p
= 



If the secondary coil has a greater number of turns than the primary, the
voltage is stepped-up (Vs > Vp) This type of arrangement is called a step-
up transformer If the secondary coil has turns less than the primary, we
have a step-down transformer Rationalised 2023-24
Physics
198
 Physical quantity
Symbol
Dimensions
Unit
Remarks
rms voltage
V
[M L
2 T
–3 A
–1]
V
V 
= 
2
vm
, 
v m 
is 
the
amplitude of the ac voltage