A galvanometer having a resistance of 20 Ω and 30 divisions on both sides has figure of merit 0.005 ampere/division. The resistance that should be connected in series such that it can be used as a voltmeter upto 15 V , is:

Question

A galvanometer having a resistance of 20 Ω and 30 divisions on both sides has figure of merit 0.005 ampere/division. The resistance that should be connected in series such that it can be used as a voltmeter upto 15 V , is: (A) 120 Ω  (B) 100 Ω  (C) 80 Ω  (D) 125 Ω

Tardigrade Admin · Accepted Answer

Current for full scale deflection =0.005× 30=0.150 A Voltage for full scale deflection =0.150× 20 V =3.0 V Resistance required to be connected in series =((15/3) - 1) 20 Ω =80 Ω

Q. A galvanometer having a resistance of $20 Ω$ and $30$ divisions on both sides has figure of merit $0.005$ ampere/division. The resistance that should be connected in series such that it can be used as a voltmeter upto $15$ $V$ , is:

$120 Ω$

$100 Ω$

$80 Ω$

$125 Ω$

Current for full scale deflection $= 0.005 \times 30 = 0.150 A$
Voltage for full scale deflection $= 0.150 \times 20 V$
$= 3.0 V$
Resistance required to be connected in series $= (\frac{15}{3} - 1) 20 Ω$
$= 80 Ω$

Q. A galvanometer having a resistance of 20Ω and 30 divisions on both sides has figure of merit 0.005 ampere/division. The resistance that should be connected in series such that it can be used as a voltmeter upto 15 V , is:

120Ω

100Ω

80Ω

125Ω