The range of an ammeter of resistance G can be increased from I to n I by connecting

A series resistance of G n + 1 Ω

A series resistance of G n - 1 Ω

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For a four pole, $16$ slot armature with two coil-side/slot having lap connected progressive winding has single turn coils. Then number of commutator segment is?

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Important Questions on Current Electricity

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Physics>Electricity and Magnetism>Current Electricity>Electrical Accessories

The range of an ammeter of resistance

G

can be increased from

I

n I

by connecting

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Electrical Accessories

A moving coil galvanometer has a coil with

175

turns and area

1 c m^{2} .

It uses a torsion band of torsion constant

10^{- 6} N m / r a d

The coil is placed in a magnetic field B parallel to its plane. The coil deflects by

1^{o}

for a current of

1 m A

The value of B (in tesla) is approximately:

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Electrical Accessories

A moving coil galvanometer has resistance

50 Ω

and it indicates full deflection at

4 m A

current. A voltmeter is made using this galvanometer and a

5 k Ω

resistance. The maximum voltage, that can be measured using this voltmeter, will be close to:

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Physics>Electricity and Magnetism>Current Electricity>Electrical Accessories

Distinguish between ammeter and voltmeter.

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Physics>Electricity and Magnetism>Current Electricity>Electrical Accessories

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:

HARD

Physics>Electricity and Magnetism>Current Electricity>Electrical Accessories

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

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Electrical Accessories

The resistance of a galvanometer is

50 o h m

and the maximum current which can be passed through it is

0.002 A .

What resistance must be connected to it in order to convert it into an ammeter of range

0 - 0.5 A ?

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Physics>Electricity and Magnetism>Current Electricity>Electrical Accessories

The diagram below shows a dual control switch circuit connected to a bulb. Copy the diagram and complete it so that the bulb is switched ON.

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Physics>Electricity and Magnetism>Current Electricity>Electrical Accessories

Sensitivity of moving coil galvanometer is

s

. If a shunt of

{(\frac{1}{8})}^{t h}

of the resistance of galvanometer is connected to moving coil galvanometer, its sensitivity becomes

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Electrical Accessories

A galvanometer having a coil resistance of

100 Ω

gives a full scale deflection, when a current of

1 mA

is passed through it. The value of the resistance, which can convert this galvanometer into ammeter giving a full scale deflection for a current of

10 A

, is:

HARD

Physics>Electricity and Magnetism>Current Electricity>Electrical Accessories

A moving coil galvanometer has 50 turns and each turn has an area

2 \times 10^{- 4} m^{2}

. The magnetic field produced by the magnet inside the galvanometer is

0.02 T

. The torsional constant of the suspension wire is

10^{- 4} N m {rad}^{- 1}

. When a current flows through the galvanometer, a full scale deflection occurs if the coil rotates by

0.2 rad

. The resistance of the coil of the galvanometer is

50 Ω

. This galvanometer is to be converted into an ammeter capable of measuring current in the range

0 - 1.0 A

. For this purpose, a shunt resistance is to be added in parallel to the galvanometer. The value of this shunt resistance, in ohms, is

α

. Write the value of

[α]

, where

[]

is the greatest integer function.

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Physics>Electricity and Magnetism>Current Electricity>Electrical Accessories

The current sensitivity of a moving coil galvanometer depends on,

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Physics>Electricity and Magnetism>Current Electricity>Electrical Accessories

To know the resistance

G

of a galvanometer by half deflection method, a battery of emf

V_{E}

and resistance

R

is used to deflect the galvanometer by angle

θ

. If a shunt of resistance

S

is needed to get half deflection the

G

R

and

S

are related by the equation:

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Physics>Electricity and Magnetism>Current Electricity>Electrical Accessories

The galvanometer deflection, when key $K_{1}$ is closed but $K_{2}$ is open, equals $θ_{0}$ (see figure). On closing $K_{2}$ also and adjusting $R_{2}$ to $5 Ω,$ the deflection in galvanometer becomes $\frac{θ_{0}}{5} .$ The resistance of the galvanometer is, then, given by [Neglect the internal resistance of battery]: