A circuit has a fuse of 5A.find the maximum number of 100W 220V lamp that can be used in a circuit.
Given Power - 100W
Given Voltage - 220V
We know
P = V*I where P = power, V = voltage and I = current
Applying this formula we get
100 = 220 * I
=> I = 100/220 = 0.4545454545..........A = 0.45A approx.
Now current required to run one lamp of 100W 220V = 0.45
Total current supply = 5A
Therefore, no. of appliances which can be used at one time - 5/0.45 = 11.1111111......... = 11.11
Since appliances cannot be taken in points, the number of appliances will be 11.
Note: It wont matter whether the lamps are connected in series or parallel. The current drawn by each lamp will be the same, i.e. the current flowing through each lamp will be the same as in series connection, and in parallel connection, since V is always the same, and the resistances of all the lamps is also the same, the current will be same.
Hope this helps!!