question_answer

A circuit contains an ammeter, a battery of 30 V and a resistance 40.8\[\Omega \]. all connected in series. If the ammeter has a coil of resistance 480\[\Omega \]. and a shunt of 20 \[\Omega \], then reading in the ammeter will be

A)  0.5A                     

B)  0.25A   

C)  2A                         

D)  1 A

Correct Answer: A

Solution :

Effective resistance of a circuit, \[{{R}_{eff}}=40.8+\frac{480\times 20}{480+20}\] \[=40.8+19.2=60\Omega \] So, current flowing across ammeter, \[I=\frac{V}{R}=\frac{30}{60}=\frac{1}{2}=0.5A\] Hence, reading of ammeter = 0.5 A