The following combination are concerned with experiments of the characterization and use of a moving coil galvanometer.
The series combination of variab resistance R, one `100 Omega` resistor and moving coil galvanometer is connected to a mobile phone charger having negligible internal resistance. The zero of the galvanometer lies the centre and the pointer can move 30 division full scale on either side depending on the directin of current. The reading of the galvanometer is 10 divisions and the voltages across the galvanometer and `100 Omega` resistor are respectively 12mV and 16 mV.
The series combination of the galvanometer with a resistnce of R is conneted across an ideal voltage supply of 12 V and this time the galvanometer shows full scale defiention of 30 divisions.
The value of R is nearly

Answer

To solve the problem step by step, we will analyze the two scenarios presented in the question.

### Step 1: Analyze the first scenario
In the first scenario, we have a moving coil galvanometer (with resistance \( R_G \)), a 100 Ω resistor, and a variable resistance \( R \) connected in series to a mobile phone charger. The voltages across the galvanometer and the 100 Ω resistor are given as 12 mV and 16 mV, respectively.

1. **Calculate the current (I) through the circuit:**
\[ V_{100} = I \times R_{100} \]
\[ 16 \text{ mV} = I \times 100 \Omega \]
\[ I = \frac{16 \times 10^{-3}}{100} = 0.16 \text{ mA} \]