JEE Advanced | 2014Current Electricity and Electrical InstrumentMedium
Question
Heater of an electric kettle is made of a wire of length L and diameter d. It takes 4 minutes to raise the temperature of 0.5 kg water by 40 K. This heater is replaced by a new heater having two wires of the same material, each of length L and diameter 2d. The way these wires are connected is given in the options. How much time in minutes will it take to raise the temperature of the same amount of water by 40 K?
Options
A.4 if wires are in parallel
B.2 if wires are in series
C.1 if wires are in series
D.0.5 if wires are in parallel
Solution
t = 
⇒ t ∝ R. R =( ρl / A), R′ =
(as d′ = 2d)
When wires are in series, R1 = R′ + R′ = 2R′ =
⇒ t′ = 
= 2 min
When wires are in parallel, R2 =
⇒ t′ = 
= 0.5 min
⇒ t ∝ R. R =( ρl / A), R′ =
(as d′ = 2d)When wires are in series, R1 = R′ + R′ = 2R′ =
⇒ t′ = = 2 minWhen wires are in parallel, R2 =
⇒ t′ = = 0.5 minCreate a free account to view solution
View Solution FreeTopic: Current Electricity and Electrical Instrument·Practice all Current Electricity and Electrical Instrument questions
More Current Electricity and Electrical Instrument Questions
During an experiment with a metre bridge, the galvanometer shows a null point when the jockey is pressed at 40.0 cm usin...In the adjacent circuit, AB is a potentiometer wires of length 40 cm no resistance per unit length 50Ω /m. As shown...An electric power line having total resistance of $2\Omega$, delivers 1 kW of power of 250 V . The percentage efficiency...In the arrangment of resistances shown below. The effective resistance between points A and B is...P, Q is a uniform wire of resistance 2000 Ω and M the mid point of PQ. A voltmeter of resistance 1000 Ω is con...