Advertisements
Advertisements
Question
A multirange voltmeter can be constructed by using a galvanometer circuit as shown in figure. We want to construct a voltmeter that can measure 2V, 20V and 200V using a galvanometer of resistance 10Ω and that produces maximum deflection for current of 1 mA. Find R1, R2 and R3 that have to be used.
Advertisements
Solution
The galvanometer can also be used as a voltmeter to measure the voltage across a given section of the circuit. For this, a very high resistance wire is to be connected in series with galvanometer. The relationship is given by Ig (G + R) – V where Ig is the range of galvanometer, G is the resistance of galvanometer and R is the resistance of wire connected in series with galvanometer.
Applying expression in different situations
For `i_G (G + R_1)` = 2 for 2 V range
For `i_G (G + R_1 + R_2)` = 20 for 20 V range
And For `i_G (G + R_1 + R_2 + R_3)` = 200 for 200 V range
By solving, we get
R1 = 1990 Ω R2 = 18 kΩ and R3 = 180 kΩ.
APPEARS IN
RELATED QUESTIONS
The combined resistance of a galvanometer of resistance 500Ω and its shunt is 21Ω. Calculate the value of shunt.
Why does a galvanometer show a momentary deflection at the time of charging or discharging a capacitor? Write the necessary expression to explain this observation.
A circular coil of 250 turns and diameter 18 cm carries a current of 12A. What is the magnitude of magnetic moment associated with the coil?
Draw a labelled diagram of a moving coil galvanometer. Describe briefly its principle and working.
Increasing the current sensitivity of a galvanometer may not necessarily increase its voltage sensitivity. Explain, giving reason.
Explain how moving coil galvanometer is converted into a voltmeter. Derive the necessary formula.
Define current sensitivity of a galvanometer.
Why does a galvanometer when connected in series with a capacitor show a momentary deflection, when it is being charged or discharged?
How does this observation lead to modifying the Ampere's circuital law?
Hence write the generalised expression of Ampere's law.
Write current sensitivity of a galvanomete S.I. unit.
Figure shows two circuits each having a galvanometer and a battery of 3V.
When the galvanometers in each arrangement do not show any deflection, obtain the ratio R1/R2.
The current sensitivity of a galvanometer is defined as ______.
A moving coil galvanometer can be converted into an ammeter by ______.
The coil of a moving coil galvanometer is wound over a metal frame in order to ______.
When a galvanometer is shunted with a 4 Ω resistance, the deflection is reduced to one-fifth. If the galvanometer is further shunted with a 2 Ω wire. The further reduction (find the ratio of decrease in current to the previous current) in the deflection will be (the main current remains the same)
A galvanometer coil bas 500 turns and each tum has an average area of 3 × 10-4 m2. If a torque of 1.5 Nm is required to keep this coil parallel to a magnetic field when a current of 0.5 A is flowing through it, the strength of the field (in T) is ______.
A moving coil galvanometer has 150 equal divisions. Its current sensitivity is 10-divisions per milliampere and voltage sensitivity is 2 divisions per millivolt. In order that each division reads 1 volt, the resistance in ohms needed to be connected in series with the coil will be ______.
A moving coil galvanometer of resistance 55 Ω produces a full scale deflection for a current of 250 mA. How will you convert it into an ammeter with a range of 0 - 3A?
To convert a moving coil galvanometer into an ammeter we need to connect a ______.
