Question 4 - Past Year - 2 Mark Questions - Chapter 12 Class 10 - Electricity (Term 2)

Last updated at May 10, 2022 by Teachoo

A student has two resistors- 2 Ω and 3 Ω. She has to put one of them in place of R2 as shown in the circuit. The current that she needs in the entire circuit is exactly 9A. Show by calculation which of the two resistors she should choose

Answer:

The current she needs in the entire circuit is 9 A.

Therefore, we choose
case 1.

So,
R
2
= 2 ohm

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Question 4 A student has two resistors- 2 Ω and 3 Ω. She has to put one of them in place of R2 as shown in the circuit. The current that she needs in the entire circuit is exactly 9A. Show by calculation which of the two resistors she should choose Case 1 :
She uses the 2 ohm resistor.
So, R2 = 2 ohm
R1 = 4 ohm
R1 & R2 are connected in parallelCase 2 :
She uses the 3 ohm resistor.
So, R2 = 3 ohm
R1 = 4 ohm
R1 & R2 are connected in parallel
Let total resistance be R
1/𝑅=1/𝑅1+1/𝑅2
1/𝑅1=1/4+1/2
1/𝑅1=(1 + 2)/4=3/4
Therefore, R = 4/3
Given, V = 12 volts
According to omh’s law
V = 𝐼/𝑅
So, I = 𝑉/𝑅Let total resistance be R
1/𝑅=1/𝑅1+1/𝑅2
1/𝑅1=1/4+1/3
1/𝑅1=(3 + 4)/12=7/12
Therefore, R = 12/7
Given, V = 12 volts
According to omh’s law
V = 𝐼/𝑅
So, I = 𝑉/𝑅= 12/((4/3) )
= ((12 × 3))/4
= 9 A= 12/((12/7) )
= ((12 × 7))/12
= 12 A
The current she needs in the entire circuit is 9 A.
Therefore, we choose case 1.
So, R2 = 2 ohm

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CA Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 12 years and a teacher from the past 16 years. He teaches Science, Accounts and English at Teachoo