Question

A 200w, 100v lamp is to be operated on 250v supply. The additional resistance required to be connected in series will be:

(a)125ohm (b)50ohm (c)75ohm (d)25ohm
​

Answer 1

Answer:

125 ohms

Explanation:

we know that the current passing  through a bulb is give by

rated power/ rated voltage=200/100=2

now to find resistance = given voltage / current =250/2=125

1.        they have given the rated power in the bulb as      200W
2. they have given the rated voltage as 100V
3. now we have to find the maximum current that can passes through that bulb so
4. max current= rated power / rated  voltage
5. then in the question the bulb is given a supply of 250V ie the supplied voltage is 250V
6. now find the resistance to be connected so that there is a potential difference of 250V ie

250/2=125ohms

Answer 2

Answer:

A 200w, 100v lamp will consume 2amps of current (using ohms law) and will have a resistance of 50 ohms(using ohms law) .