Two bulbs 25W, 100 V (upper bulb in figure) and 100 W, 200 V (lower bulb in figure) are connected in the circuit as shown in figure. Choose the correct answer.

Options

A. Heat lost per second in the circuit will be 80 J.
B. Ratio of heat produced per second in bulb will be `1:1`
C. Ratio of heat produced in branch AB to that produced in branch CD will be `1:2`.
D. Current drawn from the cell is 0.4A.

Answer

A, D

Explanation

a.,d.
Resistance of upper bulb, `R_1 = 100^2//25 = 400 Omega`
Resistance of lower bulb, `R_2 = 200^2//100 = 400 Omega`
Equivalent resistance of the circuit, `R_(eq) = 500 Omega`
Heat lost per second in the circuit is
`e^2//R_(eq) = 200^2//500 = 80Js^(-1)`
Potential difference across branches AB and CD will be same.
Hence, ratio of heat generated in them is
`Heat_(AB)/Heat_(CD) = R_(CD)/R_(AB) = 1000/500 = 2:1`
Hence, (c ) is incorrect.
Since potential difference across branches AB and CD will be
the same, but their resistances are different, so current in them
will be different. As the resistances of the bulbs are same, so
heat generated in them will be different. Hence, (b) is incorrect.
Current drawn from the cell is `e//R_(eq) = 200//500 = 0.4A`.