Solved 2023 Question Paper CBSE Class 10 Science — Question 4

(a) Given,

Power (P) = 880 W [when heating is at the maximum rate ]

Power (P) = 330 W [when heating is at the minimum rate ]

Voltage (V) = 220 V

Case I : When heating is at the maximum rate

We know,

P = VI

Substituting we get,

880 = 220 x I

I = $\dfrac{880}{220}$ = 4 A

From V = IR

Substituting we get,

220 = 4 x R

R = $\dfrac{220}{4}$ = 55 Ω

Hence, when heating is at the maximum rate, I = 4 A and R = 55 Ω

Case II : When heating is at the minimum rate

Substituting we get current (I)

330 = 220 x I

I = $\dfrac{330}{220}$ = $\dfrac{3}{2}$ = 1.5 A

Substituting we get resistance (R),

220 = 1.5 x R

R = $\dfrac{220}{1.5}$ = 1.46 Ω

Hence, when heating is at the minimum rate, I = 1.5 A and R = 1.46 Ω

(b) When the electric circuit is purely resistive, that is, a configuration of resistors only connected to a battery; the source energy continually gets dissipated entirely in the form of heat. This is called heating effect of electric current.

(c) H = I²Rt where

This is known as Joule's law of heating.