2007PPp1q28 2019PPp1q33 - Which V-I readings are for torch lamp?

2019PPP1Q33 Ans: Option B

2007PPP1Q28 Ans: Option B

Torch lamp or bulb is a non-ohmic conductor. The V-I graph has an increasing gradient indicating resistance increases. As the current through the filament of bulb increases (due to p.d across increases), temperature increases and resistance increases.

For an ohmic conductor, the graph of V against I is a straight line with constant gradient and passes through the origin.

Something to thing about:

What if there is an option E whereV increases from 0, 1, 2, 3I increases from 0, 6, 10, 12 respectively. The graph will be a typical ohmic graph, similar shape to option B, but will you choose E?

Refer to the last section of the video from 4:37 s.