1.

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» 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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