Which type of metal or alloy cannot be used to prepare a fuse wire?

Find the resistance of a bulb rated as $100 \, W - 250 \, V$.

How many joules are there in one kilowatt-hour?

$A$ $100 \text{ W}$ electric bulb is lighted for $2 \text{ hours}$ daily,and four $40 \text{ W}$ bulbs are lighted for $4 \text{ hours}$ everyday. Calculate the energy consumed (in $\text{kWh}$) in $30 \text{ days}$.

If the current $I$ through a resistor is increased by $100\%$ (assume that temperature remains unchanged), the increase in power dissipated will be ........ $\%$

Explain the following.
$(a)$ Why is tungsten used almost exclusively for the filament of electric lamps?
$(b)$ Why are the conductors of electric heating devices,such as bread-toasters and electric irons,made of an alloy rather than a pure metal?