Question

4.) A Tungsten light bulb and carbon light bulb are each connected to a power source. As the current through each bulb is increased and the resistance of each bulb is observed one can conclude that?

a.) the resistance of the Tungsten and the resistance of the carbon both remain constant.
b.) the resistance of the tungsten bulb remains constant and the resistance of the carbon bulb increases
c.) the resistance of the carbon bulb remains constant and the resistance of the tungsten bulb increases
d.) the resistance of both bulbs increases
e.) the resistance of both bulbs decreases
f.) The resistance of the tungsten bulb increases and the resistance of the carbon bulb decreases
g.) the resistance of the tungsten bulb decreases and the resistance of the carbon bulb increases
h.) none of the above

please answer and explain

Answer 1

the answer to this question is option F

The resistance of the tungsten bulb increases and the resistance of the carbon bulb decreases.

Tungsten is a metal and has a +ve thermal coefficient of resistance, ie resistance increases with a rise in temperature. This is because the electrons move more randomly inside the metal and which decreases the collision time. Collision time is inversely proportional to resistance, resistance decreases.

whereas in carbon has a -ve thermal coefficient of resistance, ie resistance decreases with temperature. This is due to the addition of more no of electrons to the conduction band from valence band as it gains energy from rising in temperature.As the number of electrons increases there the conduction increases which decreases resistance.