Question:

In an experiment on a circuit, as shown in the figure, the voltmeter shows 8V reading. The resistance of the voltmeter is 
the voltmeter shows 8V reading

Updated On: Oct 30, 2024
  • 20Ω
  • 320Ω
  • 160Ω
  • 1.44kΩ
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The Correct Option is C

Solution and Explanation

Given the values: I=10Ω8 volts=5/4=0.8 AI=8 volts10Ω​=45​=0.8 A Voltage across 5Ω5Ω: V1​=(0.8)×5=V1​=4 volts

Hence, the electromotive force (e.m.f) of the battery is equal to the voltage across 10Ω10Ω, which is:

EMF=8+4=EMF=12 voltsEMF=8+4=EMF=12 volts

Therefore, the correct option is 160Ω.

The correct option is(C): 160Ω

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Concepts Used:

Resistance

Resistance is the measure of opposition applied by any object to the flow of electric current. A resistor is an electronic constituent that is used in the circuit with the purpose of offering that specific amount of resistance.

R=V/I

In this case,

v = Voltage across its ends

I = Current flowing through it

All materials resist current flow to some degree. They fall into one of two broad categories:

  • Conductors: Materials that offer very little resistance where electrons can move easily. Examples: silver, copper, gold and aluminum.
  • Insulators: Materials that present high resistance and restrict the flow of electrons. Examples: Rubber, paper, glass, wood and plastic.

Resistance measurements are normally taken to indicate the condition of a component or a circuit.

  • The higher the resistance, the lower the current flow. If abnormally high, one possible cause (among many) could be damaged conductors due to burning or corrosion. All conductors give off some degree of heat, so overheating is an issue often associated with resistance.
  • The lower the resistance, the higher the current flow. Possible causes: insulators damaged by moisture or overheating.