Question

A small bulb has a resistance of 2 ohm when cold.it takes up a current of 0.4A from a source of 4v and then starts glowing.calculate the resistance of the bulb when it is glowing

Answer 1

The ‘resistance of the bulb’ is 5 ohm.

Given:

Resistance = 2 ohm

Current = 0.4 Ampere  

Voltage = 4 V  

According to Ohm’s law:  

$V=I \times R$

Hence: $R=\frac{V}{I}$

Plug the given value to calculate the resistance:

$R=\frac{2 V}{0.4 A}=5 \Omega$

Hence a small bulb has a resistance of 2 ohm when cold and takes up a current of 0.4A from a ‘source of 4v’ and then ‘starts glowing’ with resistance of 5 ohm.

Answer 2

5ohm

Explanation:

according to ohms law

v=i×r

r,=v÷r

so

r=2÷0.4,A

ans=,5ohm