Wheatstone Bridge & Meter Bridge — MH-CET Physics MCQs with Solutions
Free MH-CET Physics Wheatstone Bridge & Meter Bridge MCQs with step-by-step solutions (21 questions). Part of Current Electricity. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Wheatstone Bridge & Meter Bridge · easy · theory
The balance condition for a Wheatstone network with arms $P$, $Q$, $R$ and $S$ is:
A. $P + Q = R + S$
B. $\dfrac{P}{Q} = \dfrac{R}{S}$ ✓ Correct
C. $\dfrac{P}{R} = \dfrac{S}{Q}$
D. $PQ = RS$
Solution: At balance the bridge points are at equal potential, so no current passes through the galvanometer.
Q2 — Wheatstone Bridge & Meter Bridge · easy · theory
When a Wheatstone bridge is balanced, the current through the galvanometer is:
A. Half the main current
B. Maximum
C. Zero ✓ Correct
D. Equal to the main current
Solution: Balance means the two ends of the galvanometer branch are at the same potential, so no current is driven through it.
Q3 — Wheatstone Bridge & Meter Bridge · hard · theory
In a balanced Wheatstone bridge, interchanging the battery and the galvanometer:
A. Leaves the balance condition unchanged ✓ Correct
B. Destroys the balance completely
C. Requires all resistances to be doubled
D. Makes the current zero everywhere
Solution: This is the conjugate-arms property: the balance condition $\dfrac{P}{Q} = \dfrac{R}{S}$ is symmetric in the two branches.
Q4 — Wheatstone Bridge & Meter Bridge · easy · theory
A meter bridge works on the principle of:
A. The potentiometer
B. Kirchhoff's junction rule alone
C. The Wheatstone bridge ✓ Correct
D. Ohm's law alone
Solution: The uniform wire provides two of the four arms, their resistances being proportional to the lengths on either side of the null point.
Q5 — Wheatstone Bridge & Meter Bridge · medium · theory
In a meter bridge experiment, the null point should preferably be near the middle of the wire because:
A. The galvanometer is most sensitive there
B. The wire is thickest there
C. The percentage error in the measurement is then least ✓ Correct
D. The current is maximum there
Solution: Errors in reading the two lengths contribute least to the final result when the two segments are comparable.
Q6 — Wheatstone Bridge & Meter Bridge · medium · theory
Thick copper strips are used in a meter bridge in order to:
A. Increase the sensitivity of the galvanometer
B. Increase the resistance of the circuit
C. Provide mechanical support only
D. Minimise the end resistance of the connections ✓ Correct
Solution: Any extra resistance at the ends would add to the bridge arms and falsify the ratio of lengths.
Q7 — Wheatstone Bridge & Meter Bridge · easy · theory
For accurate results, the meter bridge wire must be:
A. Uniform in cross-section throughout its length ✓ Correct
B. Made of a superconducting material
C. Of a very low melting point
D. As thick as possible at one end
Solution: Only a uniform wire has resistance strictly proportional to length, which the method assumes.
Q8 — Wheatstone Bridge & Meter Bridge · medium · theory
The balance point of a Wheatstone bridge is independent of:
A. The ratio of the arms
B. The uniformity of the bridge wire
C. The values of the four resistances
D. The EMF of the cell used ✓ Correct
Solution: The balance condition involves only the ratios of the resistances, so changing the supply voltage does not shift the null point.
Q9 — Wheatstone Bridge & Meter Bridge · hard · theory
The sensitivity of a Wheatstone bridge is greatest when:
A. The galvanometer resistance is infinite
B. One resistance is very much larger than the others
C. The four resistances are of the same order of magnitude ✓ Correct
D. The cell EMF is very small
Solution: Comparable arms give the largest galvanometer deflection for a small departure from balance.
Q10 — Wheatstone Bridge & Meter Bridge · medium · numerical
In a meter bridge the balancing length is $40\text{ cm}$ from the left. If the resistance in the right gap is $6\,\Omega$, the unknown resistance in the left gap is:
A. $6\,\Omega$
B. $3\,\Omega$
C. $4\,\Omega$ ✓ Correct
D. $9\,\Omega$
Solution: $\dfrac{X}{R} = \dfrac{l}{100 - l} = \dfrac{40}{60} = \dfrac{2}{3}$, so $X = \dfrac{2}{3} \times 6 = 4\,\Omega$.
Q11 — Wheatstone Bridge & Meter Bridge · medium · numerical
In a meter bridge, balance is obtained at $20\text{ cm}$ from the left with an unknown $X$ in the left gap and $12\,\Omega$ in the right gap. The value of $X$ is:
A. $6\,\Omega$
B. $3\,\Omega$ ✓ Correct
C. $2\,\Omega$
D. $4\,\Omega$
Solution: $\dfrac{X}{12} = \dfrac{20}{80} = \dfrac{1}{4}$, so $X = 3\,\Omega$.
Q12 — Wheatstone Bridge & Meter Bridge · medium · numerical
In a meter bridge the null point is at $60\text{ cm}$ from the left. If the right gap holds $20\,\Omega$, the unknown resistance in the left gap is:
A. $13.3\,\Omega$
B. $20\,\Omega$
C. $40\,\Omega$
D. $30\,\Omega$ ✓ Correct
Solution: $\dfrac{X}{20} = \dfrac{60}{40} = 1.5$, so $X = 30\,\Omega$.
Q13 — Wheatstone Bridge & Meter Bridge · medium · numerical
A Wheatstone network has $P = 10\,\Omega$, $Q = 20\,\Omega$ and $R = 15\,\Omega$. For balance, $S$ must be:
A. $30\,\Omega$ ✓ Correct
B. $15\,\Omega$
C. $7.5\,\Omega$
D. $25\,\Omega$
Solution: $\dfrac{P}{Q} = \dfrac{R}{S} \Rightarrow \dfrac{10}{20} = \dfrac{15}{S} \Rightarrow S = 30\,\Omega$.
Q14 — Wheatstone Bridge & Meter Bridge · medium · numerical
In a meter bridge, balance occurs at $25\text{ cm}$ from the left. The ratio of the resistance in the left gap to that in the right gap is:
A. $3 : 1$
B. $1 : 4$
C. $4 : 1$
D. $1 : 3$ ✓ Correct
Solution: $\dfrac{X}{R} = \dfrac{25}{75} = \dfrac{1}{3}$.
Q15 — Wheatstone Bridge & Meter Bridge · hard · numerical
In a meter bridge with $4\,\Omega$ in the left gap and $6\,\Omega$ in the right gap, the balancing length from the left end is:
A. $40\text{ cm}$ ✓ Correct
B. $60\text{ cm}$
C. $25\text{ cm}$
D. $50\text{ cm}$
Solution: $\dfrac{4}{6} = \dfrac{l}{100 - l} \Rightarrow 400 - 4l = 6l \Rightarrow l = 40\text{ cm}$.
Q16 — Wheatstone Bridge & Meter Bridge · easy · numerical
In a meter bridge the null point is exactly at the midpoint of the wire. This means that:
A. The left gap resistance is twice the right
B. The right gap resistance is twice the left
C. The two gap resistances are equal ✓ Correct
D. The bridge cannot be balanced
Solution: At $l = 50\text{ cm}$, $\dfrac{X}{R} = \dfrac{50}{50} = 1$, so $X = R$.
Q17 — Wheatstone Bridge & Meter Bridge · hard · numerical
In a meter bridge the balance length is $l$ from the left. If the resistances in the two gaps are interchanged, the new balance length from the left is:
A. $100 - l$ ✓ Correct
B. $\dfrac{l}{2}$
C. $2l$
D. $l$
Solution: Interchanging the arms inverts the ratio, so the null point moves to the mirror-image position on the wire.
Q18 — Wheatstone Bridge & Meter Bridge · medium · numerical
A Wheatstone network has $P = 2\,\Omega$, $Q = 3\,\Omega$ and $S = 9\,\Omega$. For balance, $R$ must be:
A. $3\,\Omega$
B. $4.5\,\Omega$
C. $13.5\,\Omega$
D. $6\,\Omega$ ✓ Correct
Solution: $\dfrac{P}{Q} = \dfrac{R}{S} \Rightarrow \dfrac{2}{3} = \dfrac{R}{9} \Rightarrow R = 6\,\Omega$.
Q19 — Wheatstone Bridge & Meter Bridge · hard · numerical
In a meter bridge with $5\,\Omega$ in the left gap and $15\,\Omega$ in the right gap, the balancing length from the left is:
A. $25\text{ cm}$ ✓ Correct
B. $33\text{ cm}$
C. $75\text{ cm}$
D. $50\text{ cm}$
Solution: $\dfrac{5}{15} = \dfrac{l}{100 - l} \Rightarrow 3l = 100 - l \Rightarrow l = 25\text{ cm}$.
Q20 — Wheatstone Bridge & Meter Bridge · medium · numerical
In a meter bridge with $3\,\Omega$ in the left gap and $9\,\Omega$ in the right gap, the balancing length from the left is:
A. $75\text{ cm}$
B. $40\text{ cm}$
C. $25\text{ cm}$ ✓ Correct
D. $60\text{ cm}$
Solution: $\dfrac{3}{9} = \dfrac{l}{100 - l} \Rightarrow 3l = 100 - l \Rightarrow l = 25\text{ cm}$.
Q21 — Wheatstone Bridge & Meter Bridge · easy · numerical
A Wheatstone bridge has all four arms equal to $10\,\Omega$. The galvanometer current is:
A. Maximum
B. Equal to the cell current
C. Half the cell current
D. Zero, since the bridge is balanced ✓ Correct
Solution: $\dfrac{P}{Q} = \dfrac{R}{S} = 1$, so the bridge is balanced and no current flows through the galvanometer.