Two coils have equivalent resistance 12 Ω and 5 3 Ω respectively in series and parallel combinations. What are the resistances of the coils?

Let the resistances R 1 a n d R 2 So, R s e r i e s = 12 Ω = R 1 + R 2 ................(1) and R p a r a l l e l = 5 3 Ω = R 1 R 2 R 1 + R 2 .................(2) From (1) put R 2 = 12 - R 1 in (2) 5 3 = R 1 ( 12 - R 1 ) 12 12 R 1 - R 1 2 = 20 R 1 2 - 12 R 1 + 20 = 0 R 1 = 10 , 2 Thus, R 1 = 10 Ω a n d R 2 = 2 Ω o r R 1 = 2 Ω a n d R 2 = 10 Ω

EASY

12th West Bengal Board

IMPORTANT

Earn 100

The internal resistance of a $100 V$ battery is $5 Ω$ . Its emf as measured by a voltmeter connected across it shows $20 %$ error. What is the resistance of the voltmeter?

Important Questions on Current Electricity

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 5

Two coils have equivalent resistance

12 Ω

and

\frac{5}{3} Ω

respectively in series and parallel combinations. What are the resistances of the coils?

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 6

A battery and a series combination of resistances

2.25 Ω

and

1 Ω

are connected to a parallel combination of resistance

3 Ω

and

1 Ω

. The internal resistance of the battery is

0.1 Ω

and its emf is

2 V

. Calculate the magnitude of current flowing through the resistances.

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 7

Show that when a battery of negligible internal resistance is connected through a galvanometer of resistance

80 Ω

and

20 Ω

(in series), the current that flows through the galvanometer reduces to

\frac{1}{17}

th part of it when a shunt of

1 Ω

resistance is connected to the galvanometer.

EASY

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 8

An electric heater of

140 Ω

resistance and current carrying capacity of

1.2 A

is to be connected with

210 V

d.c. mains. Find the minimum value of additional resistance to be introduced into the circuit.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 9

Two identical cells of emf

1.5 V

are connected in series. When the combination is connected in series with a resistance and a galvanometer, the current through the circuit is

1 A

. If the two cells be connected in parallel, then the current through the circuit becomes

0.6 A

. Calculate the internal resistance of the cells.

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 10

A B C

is a triangle made up wire. The resistance of the sides

A B, B C

and

C A

are respectively

40, 60

and

100 Ω

. What is the equivalent resistance between the points

A

and

B

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 11

A lump of copper of mass

10 gms

and of density

9 gm / cc

is given. What should be the length and cross-section of the wire made from it so that its resistance is

2 ohms

. (Given specific resistance of copper is

1.8 \times 10^{- 6} Ωcm)

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 5 - Current Electricity>EXERCISE 5>Q 12

When a resistance of

7 ohms

is connected across the terminals of a cell, the current through the circuit is

1.1 amp

. When the resistance is increased to

13 ohms

, the current is

0.67 amp

. Determine the emf of the cell and its internal resistance.

The internal resistance of a 100 V battery is 5Ω. Its emf as measured by a voltmeter connected across it shows 20% error. What is the resistance of the voltmeter?

Important Questions on Current Electricity

Learn and Prepare for any exam you want !

The internal resistance of a $100 V$ battery is $5 Ω$ . Its emf as measured by a voltmeter connected across it shows $20 %$ error. What is the resistance of the voltmeter?