NCERT - Science

Book: NCERT - Science

Chapter: 12. Electricity

Subject: Physics - Class 10th

Q. No. 2 of In Text Questions-Pg-213

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Redraw the circuit of Question 1 putting an ammeter to measure the current through the resistors and a voltmeter to measure the potential difference across the 12 n resistor. What would be the reading in the ammeter and the voltmeter?

We redraw the circuit by including an ammeter circuit and a voltmeter across the 12 resistor, as shown in figure. Please note that the ammeter is always connected n series with the circuit but the voltmeter has been put in parallel with the 12 resistor

We will now calculate the current reading in the ammeter and potential difference reading in the voltmeter:

(i) Calculation of current flowing in the circuit. The three resistors of 5 , 8 and 12 are connected in series. So, net resistance in series is the sum of all the resistances.

Ans: Total resistance,

Potential difference, V = 6 V

And, Current, I = ?

We know,

Since the current in the circuit is 0.24 A, therefore, the ammeter will show reading of 0.24 A.

(ii) Calculation of potential difference across the 12 resistor. From (i) we have calculated that a current of 0.24 A flows in the circuit. Since, in series same current flows through the whole circuit. The same current of 0.24 A also flows through the 12 .

Now, for the 12 resistor:

Current, I = 0.24 A

Resistance, R = 12

And, Potential difference, V =?

We know that,

Thus, the potential difference across the 12 resistor is 2.88V. So, the voltmeter will show a reading of 2.88 V.


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