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NEET PHYSICSMOVING CHARGES AND MAGNETISMEasy

Question

A circuit contains an ammeter, a battery of 30 V30\text{ V} and a resistance 40.8 Ω40.8\,\Omega all connected in series. If the ammeter has a coil of resistance 480 Ω480\,\Omega and a shunt of 20 Ω20\,\Omega then reading in the ammeter will be :

A

0.5A

B

0.25A

C

2A

D

1A

Step-by-Step Solution

To find the ammeter reading, we first determine the total resistance of the circuit. According to the sources, an ammeter consists of a galvanometer coil and a shunt resistance connected in parallel .

  1. Calculate the ammeter resistance (RaR_a): The coil (480 Ω480\,\Omega) and shunt (20 Ω20\,\Omega) are in parallel. Their effective resistance is: Ra=Rcoil×rsRcoil+rs=480×20480+20=9600500=19.2 ΩR_a = \frac{R_{\text{coil}} \times r_s}{R_{\text{coil}} + r_s} = \frac{480 \times 20}{480 + 20} = \frac{9600}{500} = 19.2\,\Omega .

  2. Calculate the total circuit resistance (RtotalR_{\text{total}}): The ammeter and the external resistor (40.8 Ω40.8\,\Omega) are connected in series . Rtotal=Rext+Ra=40.8+19.2=60.0 ΩR_{\text{total}} = R_{\text{ext}} + R_a = 40.8 + 19.2 = 60.0\,\Omega.

  3. Apply Ohm's Law to find the current (II): The ammeter reading represents the total current flowing through the series circuit . I=VRtotal=30 V60 Ω=0.5 AI = \frac{V}{R_{\text{total}}} = \frac{30\text{ V}}{60\,\Omega} = 0.5\text{ A}.

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from MOVING CHARGES AND MAGNETISM. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSMOVING CHARGES AND MAGNETISMcircuitcontainsammeterbatteryresistance

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