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ICSE Class 10 Physics Question 26 of 27

Solved Sample Paper 1 — Question 15

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Question

Question 8(iii)

(a) A current of 1 A flows in a series circuit having an electric lamp and a conductor of 5 Ω when connected to a 10 V battery. Calculate the resistance of the electric lamp.

(b) Now, if a resistance of 10 Ω is connected in parallel with this series combination, then what change (if any) in current flowing through 5 Ω conductor and potential difference across the lamp will take place? Give reason.

Answer

(a) Given,

Current I = 1 A

Voltage V = 10 V

Resistance of conductor = 5 Ω

Resistance of lamp = Rl

Equivalent resistance Rs

= Resistance of conductor + Resistance of lamp

= 5 + Rl

A current of 1 A flows in a series circuit having an electric lamp and a conductor of 5 Ω when connected to a 10 V battery. Calculate the resistance of the electric lamp. Physics Sample Paper Solved ICSE Class 10.

According to Ohm's law V = IR

Substituting we get, 10 = 1(5+Rl)

Rl = 10 - 5 = 5 Ω

Hence, resistance of the electric lamp = 5 Ω

(b) Total resistance

1Rp=1R1+5+1101Rp=15+5+1101Rp=110+110⇒1Rp=210⇒Rp=5Ω\dfrac{1}{R_p} = \dfrac{1}{R_1 + 5} + \dfrac{1}{10} \\[0.5em] \dfrac{1}{R_p} = \dfrac{1}{5+5} + \dfrac{1}{10} \\[0.5em] \dfrac{1}{R_p} = \dfrac{1}{10} + \dfrac{1}{10} \\[0.5em] \Rightarrow \dfrac{1}{R_p} = \dfrac{2}{10} \\[0.5em] \Rightarrow R_p = 5 Ω

A current of 1 A flows in a series circuit having an electric lamp and a conductor of 5 Ω when connected to a 10 V battery. Calculate the resistance of the electric lamp. Now, if a resistance of 10 Ω is connected in parallel with this series combination, then what change (if any) in current flowing through 5 Ω conductor and potential difference across the lamp will take place? Give reason. Physics Sample Paper Solved ICSE Class 10.

Hence, Current flowing through the circuit I = 105\dfrac{10}{5} = 2A

Thus, 1A current flows through 10 Ω resistor and 1A flows through lamp and conductor, hence, there is no change in current flowing through conductor. Also there is no change in potential difference across the lamp.