Page 32 - Physics - XII

Observations

1. Given resistance of the galvanometer, G = _____ Ω
2. Given value of the fi gure of merit of the galvanometer, K = _____ amp./division
3. Total number of divisions on either side of the zero of the galvanometer, n = _____ divisions
4. Current for full scale defl ection, I = nK = _____ amp.
g
5. Range of conversion of the converted voltmeter, V = _____ volt
V
6. Value of the required series resistance, R G = _____ Ω
I g

V
7. Least count of the converted voltmeter = = _____ volt
n
8. Least count of the standard voltmeter = _____ volt

Table for the verifi cation of converted voltmeter
Reading of converted galvanometer into voltmeter Standard voltmeter Diff erence (Error)
S. Defl ection Potential diff erence reading V 2 V – V 1
2
No. θ θ V = θθ × L.C. (volt) (volt)
(division) 1 (volt)
1.

2.

3.
4.

Calculations
Compute the value of required series resistance by using the relation, R V G
I g
Result
1. The value of required high resistance to be connected in series with the galvanometer to convert it into
voltmeter of the given range = _____ Ω
2. Value of the current for full scale defl ection, I = _____ amp
g
3. As (V – V ) is very small, hence, conversion of the given galvanometer into voltmeter of the given
1
2
range is verifi ed.
Precautions
1. All the connections should be neat, clean, and tight.
2. The voltmeter used for verifi cation should be of the same range as the range of the conversion.
3. The e.m.f. of the battery should be constant.

4. The value of the required series resistance should be calculated accurately.

Sources of Error
1. The galvanometer divisions may not be of equal size.

2. The e.m.f. of the battery may not be constant.

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