Ramya wants to measure the current flowing through the circuit shown below.

Which among the four ammeters can she use for the same? Show your calculations.

Ammeter | Minimum range | Maximum range |

L | 0 mA | 1 m A |

P | 0 mA | 10 m A |

Q | 0 A | 1 A |

R | 0 A | 10 A |

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Best answer

From Ohm's law, we have

V = IR

I = V/R

given V = 12 V and R_{1} = 2 ohm, R_{2} = 8 ohm and R_{3} = 4 ohm

Therefore,

net resistance R = R_{1} + (R_{2} x R_{3})/ (R_{2} + R_{3})

= 2 + (8 x 4/8 + 4)

= 2 + 32/12

= 2 + 2.66 R

= 4.66 ohm

I = 12/4.66

I = 2.58 A

She can use ammeter S to measure the current in the circuit.