You obtain a 100 W light bulb and a 50 W light bulb. Instead of connecting them in the normal way, you devise a circuit that places them in series across normal household voltage. Which bulb glows more brightly?

50W bulb

Explanation:

Considering the relationship between power, resistance and voltage, we know that

Where R is resistance, V is voltage across the circuit and P is power

Considering 100 W power, its resistance will be

Similarly, resistance of a 50 W power will be

Clearly, the resistance of 50W is greater than resistance of 100W

For series connection, power will be given by

P=I²R

For 100W bulb, power will be

For 50W bulb, power will be

The current will be the same hence it is clear that power of 50W bulb will be more than power of 100W bulb. Therefore, the 50W bulb has more brightness.