Question

a projector lamp can be used at a maximum voltage of 60v its resistance is 20ohm the series resistance required to operate lamp from 75v supply is

Answer 1

Answer:

Final Answer: Minimum series Resistance : 5ohm

Steps and Understanding:

1) Maximum potential difference across lamp is 60V.

Internal Resistance of Lamp, r = 20ohm.

Maximum Current across it that will flow through out the. circuit,

By Ohm, 's Law,

I(max) = V(max) / r = 60/ 20 = 3A.

2) Since, 60 V is across Lamp so remaining

15 V will. be across External Resistor.

Current, I(max) = 3A.

Minimum Resistance, R = 15V/ 3 = 5ohm.

This is resistance required to sufficient use of lamp at Max Volt 60 across lamp.

hope it helps

Answer 2

V=I×20

⇒I=3A

⇒IRmin=15V

=R=15/3

Rmin=5Ω.