1. Kirchhoff's first law (junction law) is based on the conservation of:
Correct Answer: B) Charge
Kirchhoff's first law states that the algebraic sum of currents meeting at a junction is zero, based on conservation of charge.
2. Kirchhoff's second law (loop law) is based on the conservation of:
Correct Answer: A) Energy
Kirchhoff's second law states that the algebraic sum of potential differences in any closed loop is zero, based on conservation of energy.
3. For two cells in series, the equivalent emf is:
Correct Answer: A) Sum of individual emfs
For cells in series: \[E_{eq} = E_1 + E_2\]
4. For two cells in parallel, the equivalent emf is:
Correct Answer: A) \(\frac{E_1r_2 + E_2r_1}{r_1 + r_2}\)
For parallel cells: \[E_{eq} = \frac{E_1r_2 + E_2r_1}{r_1 + r_2}\]
5. Terminal voltage equals emf when:
Correct Answer: A) No current is drawn
Terminal voltage: \[V = E - Ir\], when I=0, V=E
6. Internal resistance depends on:
Correct Answer: D) All of these
Internal resistance depends on electrode geometry and electrolyte properties.
7. Wheatstone bridge balance condition:
Correct Answer: A) \(\frac{P}{Q} = \frac{R}{S}\)
This is the standard balance condition for Wheatstone bridge.
8. Maximum power transfer occurs when:
Correct Answer: C) \(R_{load} = r_{internal}\)
Maximum power transfer theorem states \(P_{max}\) occurs when \(R = r\).
9. For a cell with E=2V and r=0.5Ω, maximum current is:
Correct Answer: C) 4A
\(I_{max} = E/r = 2/0.5 = 4A\) (short circuit current)
10. In potentiometer, if balancing length for 1.5V is 60cm, for 2V it would be:
Correct Answer: C) 80cm
\(\frac{E_1}{E_2} = \frac{l_1}{l_2} \Rightarrow l_2 = \frac{2}{1.5} \times 60 = 80cm\)
11. Internal resistance can be determined using:
Correct Answer: D) Both B and C
Both potentiometer and meter bridge can be used to find internal resistance.
12. For E=1.5V, r=1Ω, R=4Ω, current is:
Correct Answer: A) 0.3A
\(I = E/(R+r) = 1.5/(4+1) = 0.3A\)
13. Terminal voltage < emf when:
Correct Answer: A) Current is drawn
\(V = E - Ir\), so V < E when I > 0 (current drawn)
14. EMF is defined as:
Correct Answer: A) Work done per unit charge
EMF is work done to move unit charge through complete circuit.
15. Power in R is maximum when:
Correct Answer: B) R=r
Maximum power transfer occurs when load resistance equals internal resistance.
16. For cells in series aiding, equivalent emf is:
Correct Answer: A) Sum of emfs
For series aiding connection, emfs add up.
17. For cells in series opposing, equivalent emf is:
Correct Answer: B) Difference of emfs
For series opposing connection, emfs subtract.
18. The internal resistance of an ideal cell is:
Correct Answer: A) Zero
An ideal cell has zero internal resistance.
19. The unit of emf is same as:
Correct Answer: C) Potential difference
EMF is measured in volts, same as potential difference.
20. In a closed loop, sum of potential drops equals:
Correct Answer: A) Sum of emfs
Kirchhoff's voltage law: \(\sum V = \sum E\) in a closed loop.
21. At a junction, sum of incoming currents equals:
Correct Answer: A) Sum of outgoing currents
Kirchhoff's current law: \(\sum I_{in} = \sum I_{out}\).
22. The potential difference across terminals of a cell when current is drawn is:
Correct Answer: C) Less than emf
\(V = E - Ir\), so V < E when current is drawn.
23. The emf of a cell is 2V and internal resistance 0.5Ω. For maximum power transfer, load resistance should be:
Correct Answer: B) 0.5Ω
For max power transfer, \(R_{load} = r_{internal} = 0.5Ω\).
24. In a circuit with multiple loops, Kirchhoff's laws provide:
Correct Answer: A) Exact solution
Kirchhoff's laws provide exact solutions for complex circuits.
25. The terminal voltage of a battery decreases with:
Correct Answer: A) Increasing current
\(V = E - Ir\), so V decreases as I increases.
26. A cell of emf E and internal resistance r is connected to an external resistance R. The current is:
Correct Answer: A) \(E/(R+r)\)
Total resistance is \(R + r\), so \(I = E/(R+r)\).
27. The potential drop across a resistor R carrying current I is:
Correct Answer: A) IR
Ohm's law: \(V = IR\).
28. In a circuit with two identical cells in parallel, the equivalent emf is:
Correct Answer: A) Same as single cell
For identical cells in parallel, emf remains same but internal resistance halves.
29. The power dissipated in external resistance R is:
Correct Answer: A) \(E^2R/(R+r)^2\)
Power in R: \(P = I^2R = \left(\frac{E}{R+r}\right)^2 R\).
30. For a cell, the ratio of terminal voltage to emf is maximum when:
Correct Answer: C) R → ∞
\(V/E = R/(R+r)\), which approaches 1 as R → ∞.
31. The internal resistance of a cell can be reduced by:
Correct Answer: D) All of these
All these methods reduce internal resistance.
32. In a circuit with two resistors in series, the current is:
Correct Answer: A) Same through both
In series, current remains same through all components.
33. The potential difference across two resistors in parallel is:
Correct Answer: A) Same across both
In parallel, potential difference remains same across all branches.
34. The equivalent resistance of two resistors R₁ and R₂ in parallel is:
Correct Answer: B) (R₁R₂)/(R₁+R₂)
Parallel resistance formula: \(R_{eq} = \frac{R_1R_2}{R_1+R_2}\).
35. The current through a conductor is directly proportional to:
Correct Answer: B) Potential difference
Ohm's law: \(I \propto V\) (for constant R).
36. The resistance of a conductor increases with:
Correct Answer: D) All of these
All these factors increase resistance: \(R = \rho\frac{L}{A}\) and metals have positive temperature coefficient.
37. The resistivity of a material depends on:
Correct Answer: C) Material type and D) Temperature
Resistivity (\(\rho\)) depends on material and temperature, not dimensions.
38. The resistance of a conductor decreases with:
Correct Answer: D) All of these
Semiconductors have negative temp coefficient, and \(R \propto \frac{L}{A}\).
39. The temperature coefficient of resistance is positive for:
Correct Answer: A) Metals
Only metals have positive temperature coefficient of resistance.
40. The resistance of a perfect conductor is:
Correct Answer: A) Zero
Perfect conductor has zero resistance.
41. The resistance of an ideal insulator is:
Correct Answer: B) Infinite
Ideal insulator has infinite resistance.
42. The unit of resistivity is:
Correct Answer: B) Ohm-meter
Resistivity has units of ohm-meter (\(\Omega m\)).
43. The conductivity is:
Correct Answer: B) Reciprocal of resistivity
Conductivity (\(\sigma\)) = 1/resistivity (\(\rho\)).
44. The unit of conductivity is:
Correct Answer: B) Siemens/meter
Conductivity has units of siemens per meter (S/m).
45. The resistance of a wire is R. If its length is doubled and area halved, new resistance will be:
Correct Answer: D) 4R
\(R' = \rho\frac{2L}{A/2} = 4\rho\frac{L}{A} = 4R\).
46. The resistance of a wire is R. If its diameter is doubled, new resistance will be:
Correct Answer: B) R/4
Area becomes 4 times, so \(R' = R/4\).
47. The resistivity of a material is \(\rho\). If its length and area both are doubled, new resistivity will be:
Correct Answer: B) \(\rho\)
Resistivity is material property, independent of dimensions.
48. The current density J is related to electric field E by:
Correct Answer: B) J = \(\sigma\)E
Microscopic form of Ohm's law: \(J = \sigma E\).
49. The drift velocity of electrons is proportional to:
Correct Answer: D) All of these
\(v_d \propto I \propto J \propto E\).
50. The mobility of charge carriers is defined as:
Correct Answer: A) Drift velocity per unit electric field
Mobility: \(\mu = \frac{v_d}{E}\).