Question

A resistance coil of 60 ohm is immersed in 42 kg of water .A current of 7A is passed through it .the rise in temperature of water per minute is

Answer 1

resistance of coil ,R = 60 ohm
mass of water , M = 42kg
current passing through it , I = 7A
time taken , t = 1 min = 60 sec

you know , heat dissipates , H = I²Rt
= 7² × 60 × 60 = 49 × 3600 J

we also know, Q = Ms ∆T
here M is the mass of water , s is specific heat capacity. and ∆T is the temperature.
so, Q = 42 × 4200 × ∆T

now, Q = H
42 × 4200 × ∆T = 49 × 3600
∆T = 1°C

hence, temperature change is 1°C

Answer 2

resistance of coil ,R = 60 ohm
mass of water , M = 42kg
current passing through it , I = 7A
time taken , t = 1 min = 60 sec

you know , heat dissipates , H = I²Rt
= 7² × 60 × 60 = 49 × 3600 J

we also know, Q = Ms ∆T
here M is the mass of water , s is specific heat capacity. and ∆T is the temperature.
so, Q = 42 × 4200 × ∆T

now, Q = H
42 × 4200 × ∆T = 49 × 3600
∆T = 1°C

hence, temperature change is 1°C

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