Question

15 all
A bulb is rated at 4W, 10V.
(a) Find the resistance of the bulb and safe current for its maximum glow.
(b)
How can you run it at 20V safely?!
(c)
Find the power consumed when two such bulbs are connected to a
5V supply in
(i) Series (ii) Parallel

Answer 1

Answer:

(a) P = 4W

V = 10V

R = V×V/P

R = 10×10/25

R = 25 ohm

(c) (i) in series

P = V*V/R

=25/60

=2.4 W

(ii) in parallel

P = V*V/R

= 25/12.5

= 2W