Question

A torch bulb is rated at 1.5 v and 500mA,calculate its resistance

Answer 1

V=1.5v
I=500mA=500*10^-3A
R=V/I
R=1.5/500*10^-3
R=1.5/0.5
R=3ohm

Answer 2

Answer:

The resistance of the bulb is  3Ω.

Explanation:

Ohm's law is the description of the relationship between current, voltage, and resistance. It states that "the amount of steady current through a material is directly proportional to the potential difference, or voltage, across the materials".

$V\propto I$

$V=RI$              (1)

Where,

V=voltage across the material

R=Resistance of the material (It is constant for a given material)

I=current flowing through the material

The values given in the question are,

V=1.5V

I=500mA=500×10⁻³A=0.5A

Putting the above values in equation (1) we get;

$1.5=R\times 0.5$

$R=3\Omega$

Hence, the resistance of the bulb is  3Ω.