Question

A galvanometer is connected in series with a $0.2\Omega$ resistor. What will be the impact on angular deflection shown by a galvanometer, if it is connected in parallel to a $0.2\Omega$ resistance?
[Consider the resistance of coil inside galvanometer to be $100\Omega$]

• A. Angular deflection will remain same
• B. Angular deflection will decrease
• C. Angular deflection will increase
• D. Can't say anything

Answer 1

The correct option is B Angular deflection will decrease

Initial case :


When galvanometer is in series with $0.2\Omega$ resistor,

$R_{eq}=0.2+100=100.2\Omega$

After connecting the galvanometer in parallel with $0.2\Omega$ resistor :


Since we know that in parallel connection the current passing through a resistance is inversely proportional to its value.

$i\propto \frac{1}{R}$

So, most of the current or larger value of current will pass through path of the least resistance i.e. through $0.2\Omega$ resistance.

$\therefore i_2>i_1$

Thus, current through the galvanometer in the second case decreases.

$\because$ Current $\propto$ deflection

Hence, deflection shown by galvanometer will decrease.

Why this question ? Tip: Current will always prefer to follow a part which offers least resistance.