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How will the reading in the ammeter A of...

How will the reading in the ammeter `A` of Fig. 6.39 be affected if another identical bulb `Q` is connected in parallel to `P` as shows. The voltage in the mains is maintained at a constant value.

A

The reading will be reduced to one-half.

B

the reading will not be affected.

C

The reading will be double of the previous one.

D

The reading will be increased fourfold.

Text Solution

Verified by Experts

The correct Answer is:
C
Resistance is halved. Current is doubled.
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The ammeter shows in Fig. 6.73. Consists of 480 Omega coil connected in parallel to 20 Omega shunt. The reading of the ammeter comes out to be 1//'**'A . What is '**'?

A fuse F_(1) is connected across a source of variable voltage and the voltage is increased gradually. The fuse blows out just when the reading of the voltmeter and ammeter reaches 1.0 V and 1.0 A respectively (see figure (i)). The experiment is repeated with another fuse F_(2) and the reading of the voltmeter and ammeter when it blows out is 2.4 V and 1.2 A respectively. (a) The two fuses are connected in parallel as shown in figure (ii). Voltage is increased gradually. find the reading of the ammeter when any one of the fuses blows out. (b) The two fuses are connected in series as shown in figure (iii). find the reading of the voltmeter at the point one of the fuses blows out.

Knowledge Check

  • Read the following text and answer the following questions on the basis of the same: Shunt resistance: The ammeter shunt is the device which provides the low resistance path to the flow of current. It is connected in parallel with the ammeter. In some ammeter the shunt is in-built inside the instrument while in others it is externally connected to the circuit. Ammeters are designed for measurement of low current. For measuring high current, the shunt is connected in parallel to the ammeter. The significant portion of the current passes to the shunt because of the low resistance path and little amount of current passes through the ammeter. The shunt is connected in parallel to the ammeter because of which the voltage drops across the meter and shunt remain the same. Thus, the movement of the pointer is not affected by the shunt. Let us consider that the current to be measured is I. The circuit has ammeter and shunt connected parallel to each other. The ammeter is designed for measurement of small current say, I_(m) . The magnitude of the current I passes through the meter is very high, and it will burn the meter. So, for measuring the current I the shunt is required in the circuit. As the shunt connects in parallel with the ammeter, thus the same voltage drops occur between them: I_(Sh)R_(SH)=I_(m)R_(m) :.R_(SH)=I_(m)R_(m)//I_(SH) Shunt current I_(SH)=I-I_(m) So, R_(SH)=I_(m)R_(m)//(I-I_(m)) :.I//I_(m)=1+(R_(m)//R_(SH)) The ratio of the total current to the current required for the movement of the ammeter coil is called the multiplying power of the shunt. :. The multiplying power =m=I//L_(m) R_(SH)=R_(m)//(m-1) The following are the requirements of the shunt. • The resistance of the shunt should remain constant with time. • The temperature of the material-should remain same even though substantial current flows through the circuit. How shunt is connected with a ammeter?

    A
    In series when connected externally
    B
    In parallel when connected externally
    C
    In parallel when connected internally
    D
    Both (B) and (C)

  • Read the following text and answer the following questions on the basis of the same: Shunt resistance: The ammeter shunt is the device which provides the low resistance path to the flow of current. It is connected in parallel with the ammeter. In some ammeter the shunt is in-built inside the instrument while in others it is externally connected to the circuit. Ammeters are designed for measurement of low current. For measuring high current, the shunt is connected in parallel to the ammeter. The significant portion of the current passes to the shunt because of the low resistance path and little amount of current passes through the ammeter. The shunt is connected in parallel to the ammeter because of which the voltage drops across the meter and shunt remain the same. Thus, the movement of the pointer is not affected by the shunt. Let us consider that the current to be measured is I. The circuit has ammeter and shunt connected parallel to each other. The ammeter is designed for measurement of small current say, I_(m) . The magnitude of the current I passes through the meter is very high, and it will burn the meter. So, for measuring the current I the shunt is required in the circuit. As the shunt connects in parallel with the ammeter, thus the same voltage drops occur between them: I_(Sh)R_(SH)=I_(m)R_(m) :.R_(SH)=I_(m)R_(m)//I_(SH) Shunt current I_(SH)=I-I_(m) So, R_(SH)=I_(m)R_(m)//(I-I_(m)) :.I//I_(m)=1+(R_(m)//R_(SH)) The ratio of the total current to the current required for the movement of the ammeter coil is called the multiplying power of the shunt. :. The multiplying power =m=I//L_(m) R_(SH)=R_(m)//(m-1) The following are the requirements of the shunt. • The resistance of the shunt should remain constant with time. • The temperature of the material-should remain same even though substantial current flows through the circuit. What will be the value of the shunt resistance if the ammeter coil resistance is 1Omega and multiplying power is 100?

    A
    `1//99Omega`
    B
    `99Omega`
    C
    `101Omega`
    D
    `1//101Omega`

  • Read the following text and answer the following questions on the basis of the same: Shunt resistance: The ammeter shunt is the device which provides the low resistance path to the flow of current. It is connected in parallel with the ammeter. In some ammeter the shunt is in-built inside the instrument while in others it is externally connected to the circuit. Manganin and Constantan are used for making the shunt of DC and AC ammeter respectively. Ammeters are designed for measurement of low current. For measuring high current, the shunt is connected in parallel to the ammeter. The significant portion of the current passes to the shunt because of the low resistance path and little amount of current passes through the ammeter. The shunt is connected in parallel to the ammeter because of which the voltage drops across the meter and shunt remain the same. Thus, the movement of the pointer is not affected by the shunt. Let us consider that the current to be measured is I. The circuit has ammeter and shunt connected parallel to each other. The ammeter is designed for measurement of small current say, I_(m) . The magnitude of the current I passes through the meter is very high, and it will burn the meter. So, for measuring the current I the shunt is required in the circuit. As the shunt connects in parallel with the ammeter, thus the same voltage drops occur between them: I_(Sh)R_(SH)=I_(m)R_(m) :.R_(SH)=I_(m)R_(m)//I_(SH) Shunt current I_(SH)=I-I_(m) So, R_(SH)=I_(m)R_(m)//(I-I_(m)) :.I//I_(m)=1+(R_(m)//R_(SH)) The ratio of the total current to the current required for the movement of the ammeter coil is called the multiplying power of the shunt. :. The multiplying power =m=I//L_(m) R_(SH)=R_(m)//(m-1) The following are the requirements of the shunt. • The resistance of the shunt should remain constant with time. • The temperature of the material-should remain same even though substantial current flows through the circuit. Materials used for making shunt of DC and AC ammeter are respectively

    A
    Manganin and Manganin
    B
    Manganin and Copper
    C
    Manganin and Constantan
    D
    Constantan and Manganin

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