S L Arora Solutions for Chapter: Current Electricity, Exercise 2: VERY SHORT ANSWER CONCEPTUAL PROBLEMS

Nichrome and copper wires of same length and same radius are connected in series. Current $I$ is passed through them. Which wire gets heated up more? Justify your answer.

A heater joined in series with a $60 \mathrm{W}$ bulb is connected to the mains. If $60 \mathrm{W}$ bulb is replaced by a $100 \mathrm{W}$ bulb, will the rate of heat produced by the heater be more, less or remain the same?

A $60 \mathrm{W}$ electric bulb connected in parallel with a room heater is further connected across the mains. If $60 \mathrm{W}$ bulb is replaced by $100 \mathrm{W}$ bulb, will the heat produced by the heater be smaller, remain the same or be larger and why?

Two $120 \mathrm{V}$ light bulbs, one of $25 \mathrm{W}$ and other of $200 \mathrm{W}$ were connected in series across a $240 \mathrm{V}$ line. One bulb burnt out almost instantaneously. Which one was burnt and why?

Equation $P=I^{2}R$ seems to suggest that the rate of joule heating in a resistor is reduced if the resistance is made less, however, the equation $P=\raisebox{1ex}{$V^2$}\!\left/ \!\raisebox{-1ex}{$R$}\right.$ seems to suggest the opposite. How do you reconcile this apparent paradox?

If three electric bulbs of $100 \mathrm{W}$, $50 \mathrm{W}$ and $25 \mathrm{W}$ connected in the electric fittings of a house are lighted by the electric supply, what will be the total power consumed?

If a battery is short-circuited by means of a heavy copper wire, its temperature rises. Why?

How does the use of a fuse wire protect the electrical installations?