12th Class Physics MCQs Preparation 2022 and Onwards (Unit:  Current Electricity : Set-1 (30 MCQs)) for National MDCAT, ECAT, FPSC, PPSC, JOB Exam, Physics Lecturer, SSC, HSSC (F.Sc.), BS, MS Exams NTS, ETS, etc..


1. A flow of 10⁷ electrons per second through a conductor produces a current of




... Answer is A. 1.6 ｘ 10⁻¹² A
I = `\frac {Q}{t}` where Q = ne = 10⁷ ｘ1.6 ｘ 10⁻¹⁹C and t = 1 s


2. The first source of e.m.f. was discovered by




... Answer is B. Volta
Alessandro Volta (in 1800s),


3. Which one of the given cells is not rechargeable?




... Answer is A. Laclanche
Laclanche is a primary cell and cannot easily be recharged after one use.


4. Which one of the given sources converts light energy into electrical energy?




... Answer is C. Photocell
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5.  Which one of the following materials is non-ohmic:




... Answer is B. Germanium
Metals are ohmic and Semiconductors and insulators are non Ohmic materials


6. What will be the resistance of the wire when its length is doubled




... Answer is C. Double
Formula for Resistance R = `\frac {ρl}{A}`


7. If the resistivity of the conductor is 2 ｘ 10⁶ Ω m then its conductivity is :




... Answer is D. 5 ｘ 10⁵ Ω⁻¹ m⁻¹
resistivity and conductivity are inversely related ie. σ = `\frac {1}{ρ}`


8. Siemen is a unit of conductance and it is equal to




... Answer is D. mho . m⁻¹
Conductance G = `\frac {1}{R}` = Ω⁻¹ = mho = Siemen


9. When the resistance of the material increases by increasing the temperature then the value of the co-efficient of resistivity will be




... Answer is C. Positive
co-efficient of resistivity 𝞪 is Positive for materials like copper, silver, tungsten, etc whose resistance increases by increasing the temperature,  and negative for that material like germanium, and silicon whose resistance decreases by increasing the temperature.


10. The unit of temperature co-efficient is




... Answer is B. °C⁻¹
ΔR = 𝞪 R₀ ΔT


11. In the presence of internal resistance of the source, which one of the following relations between the potential difference (V) and e.m.f. (E) is correct




... Answer is C. E > V
E = IR + Ir = V + Ir this means E > V


12. The unit of electromotive force is




... Answer is D. Volt
e.m.f is a special type of potential difference known as electromotive force (emf). The emf is not a force.


13. The source of e.m.f. transfers its maximum power to the external circuit when (r = internal resistance, R = load resistance)

... Answer is B. r = R
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14.  Kirchhoff's 1st law is based upon the law of conservation of




... Answer is B. Charge
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15. The node in an electric circuit which has zero potential is known as




... Answer is D. Datum node
Zero potential is known as the Datum node


16.. When the direction of current is from the negative to positive terminal of the battery then 'E' is taken as




... Answer is C. Positive
When the direction of current is from the negative to positive terminal of the battery there is a rise in potential and E is taken positive and vice versa.


17. If the current passes through a resistor in an anticlockwise direction. Then the electric potential will be :




... Answer is C. Raised
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18. An electrical device that controls the current is known as




... Answer is B. Rheostat
-----Check definition


19. The electrical device which is being used to compare the e.m.f. of two cells is known as




... Answer is C. Potentiometer
Check definition


20. In a Wheatstone bridge method, the bridge is said to be balanced, when the current through the galvanometer is




... Answer is B. 0 A
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21. When a potentiometer is used for the measurement of the voltage of an unknown source, the power consumed in the circuit of the unknown source under null conditions is




... Answer is C. ideally zero.
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22. In order to achieve high accuracy, the slide wire of a potentiometer should be




... Answer is A. As long as possible
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23. Thermocouple is an arrangement of two different metals that is




... Answer is A. To convert heat energy into electrical energy
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24. The powers of two electric bulbs are 100 w and 200 w. Which are connected to the power supply of 220 V. The ratio of the resistance of their filament will be




... Answer is B. 2:1
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25.  The resistivity of two wires is 𝝆₁ and 𝝆₂ which are connected in series. If their dimensions are the same then the equivalent resistivity of the combination will be




... Answer is C. `\frac {ρ₁ + ρ₂}{2}`
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26. A wire of uniform cross-section A, length L, and resistance R is cut into two equal parts. The resistivity of each part will be




    ... Answer is C. remains the same
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    27. How much voltage is required to make 2A flow through a resistance of 8 Ω? : :




    ... Answer is C. 16 A Ω
     V = R I


    28. A proton is about 1840 times heavier than an electron. When accelerated by a potential difference of 1 kV, it's kinetic energy will be:




    ... Answer is A. 16R
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    29. 10⁶ electrons are moving through a wire per second, and the current developed is




    ... Answer is C. 1.6 ｘ 10⁻¹³ A
    I = `\frac {Q}{t}` where Q = ne = 10⁶ ｘ1.6 ｘ 10⁻¹⁹C and t = 1 s


    30. Resistance of a wire is r ohms. The wire is stretched to double its length, then its resistance in ohms is




    ... Answer is B. 4r
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