Question

The measurement of voltmeter in the following circuit is

• A. 2.25 V
• B. 4.25 V
• C. 2.75 V
• D. 6.25 V

Hint:

The potential difference across each resistor in a parallel combination of resistance is the same.

Answer 1

The Correct Option is A

The correct answer is Option A) 2.25 V

From the figure, the resistance of the voltmeter 40 \(\Omega\)  and resistance of the resistor 60 \(\Omega\) are in parallel.

 \(\therefore\quad\)Equivalent resistance \(=\frac{60\times40}{60+40}=\frac{60\times40}{100}=24\,\Omega\) 

The total current in the circuit, I \(=\frac{6\,V}{\left(40+24\right)\,\Omega}=\frac{6}{64}=\frac{3}{32}\,A\) 

The voltmeter reads potential differences across the resistance 60 \(\Omega\) connected in parallel to it.

 \(\therefore\quad\) Voltmeter reading = \(I\times R_{eq}\) \(=\frac{3}{32}\times24=\frac{9}{4}V=2.25\,V\)

Discover More from Chapter: Current Electricity

Answer 2

The correct answer is Option A) 2.25 V

Real Life Applications

Some real-life examples of Wheatstone Bridge are 
1. Load cells: It is used to measure weight. This device contains a Wheatstone bridge that measures the change in resistance of a strain gauge when a load is applied. 
2. Pressure sensors: It is a device that measures the pressure. This device contains a Wheatstone bridge that measures the change in resistance of a piezoresistive element when pressure is applied. 
3. Gas sensors: This device is used to measure the concentration of a gas. It contains a Wheatstone bridge that measures the change in resistance of a gas-sensitive element when exposed to the gas.

Question can also be asked as

1. What is the voltage reading across 60Ω in the circuit shown? 
2. What is the potential difference across 60Ω in the circuit shown? 
3. What is the reading of the voltmeter in the circuit shown? 
4. How much voltage is measured across 60Ω in the circuit shown? 
 

Answer 3

The correct answer is Option A) 2.25 V

A single resistor that draws the same current as the given combination of resistors when the same potential difference is applied across its ends is called equivalent resistance.

Equivalent Resistance in Series Combination of Resistors

• If two or more resistances are connected in series, then the formula for equivalent resistance is given by \(R_{eq}=R_1+R_2+R_3+.........\)
• In a series combination of resistors, the same current flows through all resistors when the same potential difference across the combination.

Equivalent Resistance in Parallel Combination of Resistors

• If two or more resistances are connected in parallel, then the formula for equivalent resistance is given by \(\frac{1}{R_{eq}}=\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_3}+.........\)
• In a parallel combination of resistors, the potential difference across each resistance is the same and is equal to the applied potential across the combination.

Ohm's Law

• According to Ohm's law, the current flowing through the conductor is directly proportional to the potential difference across its two ends provided that the physical condition remains the same.
• The formula of Ohm's law is \(V=IR\).

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