MEDIUM

Earn 100

Explain how a moving coil galvanometer is converted into voltmeter. Derive the necessary formula.

Important Questions on Moving Charges and Magnetism

HARD

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

A galvanometer of resistance

100 Ω

has

50

divisions on its scale and has sensitivity of

20 μ A / d i v i s i o n

. It is to be converted to voltmeter with three ranges, of

0 - 2 V, 0 - 10 V

and

0 - 20 V .

The appropriate circuit to do so is:

EASY

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

A galvanometer with its coil resistance

25 Ω

requires a current of

1 mA

for its full deflection. In order to construct an ammeter to read up to a current of

2 A

the approximate value of the shunt resistance should be:

HARD

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

Two identical moving coil galvanometer have

10 Ω

resistance and full scale deflection at

2 μ A

current. One of them is converted into a voltmeter of

100 m V

full scale reading and the other into an Ammeter of

1 m A

full scale current using appropriate resistors. These are then used to measure the voltage and current in the Ohm's law experiment with

R = 1000 Ω

resistor by using an ideal cell. Which of the following statement(s) is/are correct?

EASY

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

The number of turns in a coil of Galvanometer is tripled, then

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

How is a galvanometer converted to an ammeter?

HARD

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

A galvanometer having a coil resistance

100 Ω

gives a full scale deflection when a current of

1 m A

is passed through it. What is the value of the resistance which can convert this galvanometer into a voltmeter given full scale deflection for a potential difference of

10 V ?

EASY

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

A

B

and

C

are voltmeters of resistance

R

1 .5 R

and

3 R

respectively as shown in the figure. When some potential difference is applied between

X

and

Y

, the voltmeter readings are

V_{A}, V_{B}

and

V_{C}

respectively. Then:
Question Image

EASY

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

10 V

battery with internal resistance

1 Ω

and a

15 V

battery with internal resistance

0.6 Ω

are connected in parallel to a voltmeter (see figure). The reading in the voltmeter will be close to:

Question Image

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

Derive the expression for the torque acting on the rectangular current carrying coil of a galvanometer. Why is the magnetic field made radial?

EASY

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

Define current sensitivity of a galvanometer. Write its expression.

HARD

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

A student uses the resistance of a known resistor ( $1 Ω$ ) to calibrate a voltmeter and an ammeter using the circuits shown below. The student measures the ratio of the voltage to current to be $1 \times 10^{3} Ω$ in circuit
(a) and $0.999 Ω$ in circuit (b). From these measurements, the resistance (in $Ω$ ) of the voltmeter and ammeter are found to be close to

Question Image

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

How do you convert a moving coil galvanometer into an ammeter?

EASY

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

A circuit contains an ammeter, a battery of 30 v and a resistance 40.8 ohm all connected in series. If the ammeter has coil of resistance 480 ohm and a shunt of 20 ohm, the reading in the ammeter will be:

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

A moving coil galvanometer allows a full scale current of

10^{- 4} A

. A series resistance of

2 \times 10^{4} Ω

is required to convert the galvanometer into a voltmeter of range

0 - 5 V

. Therefore, the value of shunt resistance required to convert the above galvanometer into an ammeter of range

0 - 10 m A

is:

EASY

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

This question has

Statement I

and

Statement II

. Of the four choices given after the Statements, choose the one that best describes the two Statements.

Statement - I :

Higher the range, greater is the resistance of ammeter.

Statement - II :

To increase the range of ammeter, additional shunt needs to be used across it.

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

50 Ω

resistance is connected to a battery of

5 V

. A galvanometer of resistance

100 Ω

is to be used as an ammeter to measure current through the resistance, for this a resistance

r_{S}

is connected to the galvanometer. Which of the following connections should be employed if the measured current is with in

1 %

of the current without the ammeter in the circuit?

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

A galvanometer has a 50 division scale. Battery has no internal resistance. It is found that there is deflection of 40 divisions when $R.B. = 2400 Ω .$ Deflection becomes 20 divisions when resistance taken from resistance box is 4900 Ω. Then we can conclude :

Question Image

Note: This question is awarded as the bonus. Now the question is corrected.

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

A galvanometer, whose resistance is

50 ohm

, has

25

divisions in it. When a current of

4 \times 10^{- 4}

A passes through it, its needle (pointer) deflects by one division. To use this galvanometer as a voltmeter of range

2.5 V

it should be connected to a resistance of:

MEDIUM

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

Distinguish between ammeter and voltmeter.

EASY

Physics>Electricity and Magnetism>Moving Charges and Magnetism>Electrical Instruments

When a current of

5 mA

is passed through a galvanometer having a coil of resistance

15 Ω

, it shows full-scale deflection. The value of the resistance to be put in series with the galvanometer to convert it into a voltmeter of range

0 - 10 V

is:

Explain how a moving coil galvanometer is converted into voltmeter. Derive the necessary formula.

Important Questions on Moving Charges and Magnetism

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