Class 12
12 Mins
Class 12th Board Exam Physics Practice Set 1
Master electrostatics and optics numericals and conceptual questions for board exams.
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Question #1
Medium
A current of 2 A flows through a resistor of 4 Ω. What is the potential difference across it?
Correct Answer: Option C
Explanation: Using Ohm's Law, V = IR = 2 × 4 = 8 V.
Memory Trick: VIR Triangle: Cover V → I × R.
Exam Tip: Always identify the given values before applying Ohm's Law.
Question #2
Medium
Why does sound exhibit greater diffraction than light?
Correct Answer: Option B
Explanation: Diffraction becomes significant when wavelength is comparable to obstacle size. Sound has much larger wavelengths than visible light.
Memory Trick: Large wavelength = Large bending.
Exam Tip: Wavelength-based conceptual questions are common in board exams.
Question #3
Medium
What is the SI unit of electric field intensity?
Correct Answer: Option B
Explanation: Electric field intensity is measured in Newton per Coulomb (N/C).
Memory Trick: Force per Charge = N/C.
Exam Tip: Remember that V/m is also an equivalent unit.
Question #4
Medium
The binding energy of a nucleus is related to mass defect by which equation?
Correct Answer: Option C
Explanation: Einstein's mass-energy equivalence gives Binding Energy = Δm × c².
Memory Trick: Mass defect becomes energy through c².
Exam Tip: The formula is frequently asked directly.
Question #5
Medium
In the photoelectric effect, increasing the intensity of light increases the:
Correct Answer: Option C
Explanation: Intensity affects the number of emitted electrons, not their maximum kinetic energy.
Memory Trick: Intensity = Count, Frequency = Energy.
Exam Tip: Don't confuse intensity with frequency.
Question #6
Medium
An extrinsic semiconductor is obtained by:
Correct Answer: Option C
Explanation: Doping introduces impurities that increase conductivity.
Memory Trick: Extra impurity = Extrinsic.
Exam Tip: Know both N-type and P-type doping.
Question #7
Medium
Two particles have equal momentum. What can be said about their de Broglie wavelengths?
Correct Answer: Option B
Explanation: Since λ = h/p, equal momentum means equal wavelength.
Memory Trick: Same p → Same λ.
Exam Tip: Remember the direct relation between momentum and wavelength.
Question #8
Medium
Which law states that the algebraic sum of currents entering a junction equals the algebraic sum leaving it?
Correct Answer: Option C
Explanation: Kirchhoff's Current Law (KCL) follows conservation of charge.
Memory Trick: Junction = Current Law.
Exam Tip: KCL applies only at junctions.
Question #9
Medium
The terminal voltage of a cell becomes less than its EMF because of:
Correct Answer: Option B
Explanation: Terminal voltage = EMF − Ir, where r is internal resistance.
Memory Trick: Inside resistance reduces outside voltage.
Exam Tip: Watch for numerical questions using V = E − Ir.
Question #10
Medium
Which electromagnetic wave has the shortest wavelength among these?
Correct Answer: Option D
Explanation: Gamma rays have the highest frequency and shortest wavelength in the electromagnetic spectrum.
Memory Trick: Gamma = Greatest frequency.
Exam Tip: Memorize the EM spectrum order from Radio to Gamma.
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