Home › ISC Class 12 › Physics › Current Electricity › A heater rated to dissipate power P is run from …
A heater rated to dissipate power P is run from a fixed supply. If its resistance R is halved (voltage unchanged), the power it dissipates becomes
AP/4
BP/2
C2P
D4P
Answer & Solution
Correct answer: C. 2P
1. At fixed voltage V, use $P = V^2/R$.
2. So at constant V, power is inversely proportional to R.
3. Halving R doubles the power: new power $= 2P$.
4. Using $P = I^2 R$ here is a trap because I changes when R changes; P/4 and P/2 misapply that form.
_Source: NCERT Class 12 Physics Ch 3 "Current Electricity", p.12_
Related questions
The reactance of a capacitor $C$ at frequency $f$ in an a.c. circuit is:A bird perched on a single high voltage wire is unharmed because:The two conservation laws embodied in Kirchhoff's rules are conservation of:The resistance offered by the cell itself is called:Which device detects the current in a Wheatstone bridge?In a Wheatstone bridge, the source is connected across the:The Wheatstone bridge is made up of how many resistors?At a junction, the current entering equals the current: