Electronic Ammeter

Q. In order to measure the direct current in a wire, 5 A range ammeter is connected in series with it and indicates 4 amperes. When the 5 A range ammeter is replaced by 10 A range ammeter, the reading is 4.2 A. Both meter are known to be accurate and each produces full scale deflection for a 50 mV instrument drop. The value of current in the wire when neither meter is in the circuit is _______A.

1. 4.42
2. 44.2
3. 0.442
4. 4.2

Q.

In a Wheatstone bridge, all four arms have equal resistance $R$. If the resistance of the galvanometer arm is also $R$, the equivalent resistance of the combination is

1. $R$

2. $2R$

3. $\frac{R}{2}$

4. $\frac{R}{4}$

Q. An ammeter that has an internal resistance of 100 $\Omega$ is used to measure the current through resistor $R_3$ as shown in figures below. The percentage error caused due to meter loading is _____%.

1. 0.625
2. 6.25
3. 5
4. 0.25

Q. In a parallel combination of two milli-ammeters with full scale deflection 10 mA and 100 mA shows reading of 4 mA and 24 mA respectively. The ratio of their internal resistance will be

1. 10 : 1
2. 1 : 10
3. 6 : 1
4. 1 : 6

Q. The circuit shown below incorporates a permanent magnet coil milli-ammeter of range 0-1 mA having a series resistance of $10k\Omega .$ Assuming constant diode forward resistance of $50k\Omega ,$ a forward diode drop of 0.7 V and infinite reverse diode resistance for each diode, the reading of the meter in mA is

1. 0.45
2. 0.5
3. 0.7
4. 0.9