Obtain the relation R 1 R 2 = R 3 R 4 for a Wheatstone’s bridge. The symbols have their standard meanings.

If the wheat stone bridge is balanced, No current in arm CD. So, Applying KVL in loop ACDA I 1 R 1 - I 2 R 3 = 0 ⇒ I 1 R 1 = I 2 R 3 . . . . . . . . . . . . . . . ( 1 ) Similarly Applying KVL in loop CBDC , I 1 R 2 - I 2 R 4 = 0 ⇒ I 1 R 2 = I 2 R 4 . . . . . . . . . . . . ( 2 ) Dividing (1) by (2) R 1 R 2 = R 3 R 4

E M B I B E

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 6 - DC Circuits and Measurements>QUESTIONS>Q 7

HARD

12th ICSE

IMPORTANT

Earn 100

$n$ identical cells each of emf $E$ and internal resistance $r$ are connected in series to form a row. m such rows are connected in parallel to form a battery of $N = mn$ cells. This battery is connected to an external resistance $R$ . $(i)$ What is the emf of this battery and how much is its internal resistance?

Important Questions on DC Circuits and Measurements

HARD

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 6 - DC Circuits and Measurements>QUESTIONS>Q 7

n

Cells each of emf

E

and internal resistance

r

are connected in series to form a row. m such rows are connected in parallel to form a battery of

N = mn

Cells. This battery is connected to an external resistance:

R

. Show that current

I

flowing through the external resistance

R

is given by

I = \frac{N_{e}}{mR + nr}

HARD

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 6 - DC Circuits and Measurements>QUESTIONS>Q 8

n

identical cells, each of emf E and internal resistance

r

, are connected in series to a resistor

R

. Deduce an expression for the internal resistance

r

of one cell in terms of the current

I

in the circuit.

HARD

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 6 - DC Circuits and Measurements>QUESTIONS>Q 9

Obtain the relation

\frac{R_{1}}{R_{2}} = \frac{R_{3}}{R_{4}}

for a Wheatstone’s bridge. The symbols have their standard meanings.

HARD

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 6 - DC Circuits and Measurements>QUESTIONS>Q 9

Obtain the balancing condition for the Wheatstone bridge arrangement as shown in figure below :
Question Image

HARD

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 6 - DC Circuits and Measurements>QUESTIONS>Q 10

Draw a circuit diagram for comparing two resistances using a metre bridge. Give the principle of the experiment. Why is the method suitable for two resistances of the same order of magnitude?

HARD

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 6 - DC Circuits and Measurements>QUESTIONS>Q 11

With a circuit diagram, explain briefly how a metre-bridge can be used to find the resistance of a given wire. State the formula used.

HARD

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 6 - DC Circuits and Measurements>QUESTIONS>Q 12

Explain with diagram, the principle of a potentiometer. How can its sensitivity be increased? Why is it superior to a voltmeter?

HARD

12th ICSE