Advertisements
Advertisements
Question
A galvanometer shows full-scale deflection for current Ig. A resistance R1 is required to convert it into a voltmeter of range (0 - V) and a resistance R2 to convert it into a voltmeter of range (0 - 2V). Find the resistance of the galvanometer.
Advertisements
Solution
In the first case the potential difference between A and B,
`V = I_gR_1 + I_gG`
`I_g = V/(R_1 + G)`
Where G = Resistance of galvanometer
∴ `R_1 + G = V/I_g`
`R_1 = V/(Ig) - G`
⇒ G = `V/(Ig) - R_1`
In the second case,
`I_g = V/(R_2 + G)`
R2 is the Resistance required to change the range from 0 - 2V.
`I_g = (2V)/(R_2 + G)`
`R_2 + G = (2V)/I_g`
`R_2 = (2V)/I_g - G`
⇒ R = `(2V)/I_g - R_2`
Hence, the resistance of the galvanometer is respectively `V/(Ig) - R_1` and `(2V)/(Ig) - R_2`.
APPEARS IN
RELATED QUESTIONS
The combined resistance of a galvanometer of resistance 500Ω and its shunt is 21Ω. Calculate the value of shunt.
Increasing the current sensitivity of a galvanometer may not necessarily increase its voltage sensitivity. Explain, giving reason.
Two moving coil meters, M1 and M2 have the following particulars:
R1 = 10 Ω, N1 = 30,
A1 = 3.6 × 10–3 m2, B1 = 0.25 T
R2 = 14 Ω, N2 = 42,
A2 = 1.8 × 10–3 m2, B2 = 0.50 T
(The spring constants are identical for the two meters.)
Determine the ratio of
- current sensitivity and
- voltage sensitivity of M2 and M1.
Why is it necessary to introduce a radial magnetic field inside the coil of a galvanometer?
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 ______.
Explain in brief the basic construction of a moving-coil table galvanometer whit a neat labelled diagram.
A galvanometer of resistance 100 Ω gives a full-scale deflection for a potential difference of 200 mV.
- What must be the resistance connected to convert the galvanometer into an ammeter of the range 0-200 mA?
- Determine resistance of the ammeter.
The use of a radial magnetic field, in which \(\sin\theta = 1\) at all positions, produces a galvanometer scale deflection that is:
A voltmeter is connected across a component:
In a circuit with a 3 V source and a 3 Ω resistor, the galvanometer \((R_G = 60\ \Omega)\) is converted into an ammeter using a shunt resistance \(r_s = 0.02\ \Omega\). The measured current is approximately:
