Question

A car bulb connected to a 12 volt battery draw 2 A current when glowing. What is the resistance of the filament of the bulb?

• A. $3\Omega$
• B. $6\Omega$
• C. $9\Omega$
• D. $24\Omega$

Answer 1

The correct option is B $6\Omega$

Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance, one arrives at the usual mathematical equation that describes this relationship, I = V/R.
Rewriting this relation we arrive at $R=\frac{V}{I}=\frac{12V}{2A}=6ohms$.
Hence the resistance of the filament of the car bulb is 6 ohms.
There will be less resistance in the car bulb if the current or voltage does not flow in the circuit.