88 free MCQs on Current Electricity, each with its own worked answer and explanation. Ohm's law, resistors, Kirchhoff's laws, Wheatstone bridge, and cells.
Take the timed Current Electricity chapterwise test →88 practice questions on Current Electricity, sorted Easy → Hard. Try each one first, then open its answer page for the worked explanation. Want the full theory first? Read the Current Electricity notes.
In series, the same current flows through both resistors; in parallel, the current splits between branches and the voltage across each resistor is the same.
Q1.
A device that does NOT obey Ohm's law is called:
Q2.
A conductor whose resistance stays constant and whose V-I graph is a straight line through the origin is described as:
Q3.
The direction of conventional current in a metallic conductor is:
Q4.
Two identical cells, each having emf E and internal resistance r, are connected in parallel with the same polarity. Their equivalent internal resistance is:
Q5.
A Wheatstone bridge is balanced. If the resistance of the galvanometer branch is changed while all four arm resistances remain unchanged, the balance condition:
Q6.
A cell is being charged by an external source. If its emf is E and charging current is I, with internal resistance r, the terminal voltage of the cell is:
Q7.
For identical cells connected in parallel, the arrangement is particularly useful when the external circuit requires:
Q8.
Electric current is defined as:
Q11.
Resistance of a wire is proportional to:
Q12.
Two resistors of 2 ohm and 4 ohm are in series. Total resistance:
Q13.
Two resistors of 4 ohm and 4 ohm are in parallel. Equivalent resistance:
Q14.
Power dissipated in a resistor R carrying current I:
Q15.
Kirchhoff's current law (KCL) states that at any junction:
Q16.
Kirchhoff's voltage law (KVL) states that in any closed loop:
Q17.
A battery has EMF = 12 V and internal resistance = 2 ohm. With external resistance 10 ohm, terminal voltage is:
Q18.
Resistivity depends on:
Q19.
Electric energy consumed in 1 hour by a 1 kW appliance:
Q20.
The material with lowest resistivity is best for:
Q21.
Ammeter is connected in _____ in a circuit:
Q22.
Voltmeter is connected in _____ in a circuit:
Q23.
If a bulb rated 100 W, 220 V is connected to 110 V supply, power consumed:
Q24.
The drift velocity of electrons in a conductor is of the order:
Q25.
What is the resistance of an ideal ammeter?
Q26.
What is the resistance of an ideal voltmeter?
Q27.
Wheatstone bridge is used to measure:
Q28.
Which of the following is a non-ohmic device whose V-I graph is not a straight line?
Q29.
For a material such as GaAs, the same value of voltage can correspond to more than one value of current. This illustrates that:
Q30.
Two identical cells, each of emf 2 V and internal resistance 1 Ω, are connected in parallel with the same polarity to a 4 Ω resistor. What current flows through the resistor?
Q31.
A wire has resistivity 1.7 × 10<sup>-8</sup> Ω m, length 2 m and cross-sectional area 0.5 mm<sup>2</sup>. What is its resistance?
Q32.
A cell of emf 12 V and internal resistance 1 Ω is connected to 5 Ω and 10 Ω resistors in parallel. What current flows through the 10 Ω resistor?
Q33.
A copper conductor contains 8.5 × 10<sup>28</sup> free electrons per m<sup>3</sup>. If a current of 1.36 A flows through a cross-sectional area of 1.0 mm<sup>2</sup>, what is the electron drift speed? Take e = 1.6 × 10<sup>-19</sup> C.
Q34.
Two wires of the same material have lengths 2 m and 1 m and cross-sectional areas 1 mm<sup>2</sup> and 2 mm<sup>2</sup>, respectively. They are connected in parallel. What is the ratio of currents through the first and second wires?
Q35.
In a Wheatstone bridge, P/Q = R/S for balance. If P=10, Q=5, R=20, find S for balance:
Q36.
A wire of resistance R is stretched to double its length. New resistance:
Q37.
A potentiometer has a long wire. It is used to measure EMF because:
Q38.
Current through 6 ohm resistor in parallel combination of 3 ohm and 6 ohm connected to 12 V:
Q39.
Effective resistance between A and B: two 6 ohm resistors in series, then in parallel with 12 ohm resistor:
Q40.
When batteries of EMF E<sub>1</sub> and E<sub>2</sub> (E<sub>1</sub> > E<sub>2</sub>) are connected in series opposing (positive terminals facing each other):
Q41.
Power delivered to external load is maximum when:
Q42.
Three resistors 1, 2, 3 ohm in series across 6 V. Voltage across 3 ohm:
Q43.
A 100 W, 200 V bulb and 60 W, 200 V bulb in series across 200 V. Which is brighter?
Q44.
Resistivity of semiconductor with temperature:
Q45.
In a circuit, 5 A flows through 3 ohm and 2 ohm in series. Potential drop across 3 ohm:
Q46.
Conductance (G) is related to resistance (R) by:
Q47.
A meter bridge is balanced when X/Y = l1/(100-l1) where l1 is balance length. If l1 = 40 cm and Y = 30 ohm, X equals:
Q48.
Temperature coefficient of resistance alpha for copper is positive. This means:
Q49.
What happens to total resistance when more resistors are added in parallel?
Q50.
In a battery, EMF is the work done per unit charge:
Q51.
For a long potentiometer wire, balance point is at 40 cm for a standard cell of 1.02 V. EMF of another cell balancing at 50 cm:
Q52.
Heating element of an electric iron is made of:
Q53.
A cell of EMF 2 V and internal resistance 0.5 ohm. Short circuit current is:
Q54.
Two bulbs of 40 W and 60 W are connected in parallel to 220 V. Which draws more current?
Q55.
Two cells of emf 10 V and 4 V, each having internal resistance 2 Ω, are connected to a common 2 Ω resistor in two adjacent loops. The cells drive currents clockwise in their respective loops. What is the current through the common resistor?
Q56.
Two cells of emf 2 V and 1 V, each with internal resistance 1 Ω, are connected in parallel with the same polarity across a 2 Ω load. What is the current supplied by the combination to the load?
Q57.
Two wires of the same material are connected in series across a 12 V source. Their lengths are 2 m and 3 m, while their cross-sectional areas are 1 mm<sup>2</sup> and 4 mm<sup>2</sup>, respectively. What is the ratio of power dissipated in the first and second wires?
Q58.
A wire of resistance 16 Ω is cut into four equal pieces. Two pieces are connected in parallel to form one branch and the other two are connected in parallel to form a second branch. The two branches are then connected in series across an 8 V source. What is the total power consumed?
Q59.
A cell of emf 10 V and internal resistance 2 Ω supplies a load. When the load resistance changes from 3 Ω to 8 Ω, what is the ratio of the powers delivered to the load in the two cases?
Q60.
In a circuit, R<sub>1</sub>=5 ohm and R<sub>2</sub>=10 ohm in parallel, then in series with R<sub>3</sub>=5 ohm and battery 15 V (no internal resistance). Current through R<sub>2</sub>:
Q61.
A galvanometer of 100 ohm and full scale 1 mA is to be converted to ammeter for 1 A. Shunt needed:
Q62.
A galvanometer of 50 ohm, 2 mA FSD is converted to voltmeter reading 50 V. Series resistance needed:
Q63.
A network has 12 resistors each of 1 ohm forming a cube. Resistance between opposite corners:
Q64.
Temperature coefficient of resistance of a material is 0.004/K. At 0 degrees C resistance is 100 ohm. At 100 degrees C:
Q65.
Kirchhoff's law is applied to a complex network. The minimum number of equations needed for a network with n junctions and b branches:
Q66.
In a potentiometer, a cell of EMF 1.5 V and internal resistance 5 ohm balances at 300 cm. When cell is shunted by 10 ohm, balance shifts to:
Q67.
A circuit has 3 batteries E<sub>1</sub>=6V r<sub>1</sub>=1, E<sub>2</sub>=4V r<sub>2</sub>=1, E<sub>3</sub>=2V r<sub>3</sub>=1 connected with same polarity. Resistance R=3 ohm in loop. Current:
Q68.
Heat developed in a resistor R<sub>1</sub> in series with R<sub>2</sub> (R<sub>1</sub>:R<sub>2</sub> = 1:2) in time t:
Q69.
In the Star-Delta transformation, a star configuration with each arm R ohm is equivalent to delta with each arm:
Q70.
Mobility of charge carriers increases when:
Q71.
A 2V cell with internal resistance 1 ohm is connected to a 3 ohm resistance. Heat produced in 1 minute:
Q72.
Current density J is related to electric field E and conductivity sigma by:
Q73.
A potentiometer wire 4 m long, resistance 4 ohm, drives 2 A. Potential gradient per cm:
Q74.
Efficiency of energy transfer from source to load is maximized when:
Q75.
In a network of resistors, we can use superposition. Current due to source E<sub>1</sub> alone (E<sub>2</sub> removed/short-circuited) in a branch is I<sub>1</sub>. Due to E<sub>2</sub> alone it is I<sub>2</sub>. Actual current:
Q76.
A capacitor C and resistor R in series are connected to a battery V. At t=0, switch is closed. Initial current:
Q77.
Resistance between two opposite faces of a cube of material with resistivity rho and side a:
Q78.
A student has resistors of 1, 2, 3 ohm. Number of distinct resistance values possible:
Q79.
In a circuit, Thevenin theorem replaces any linear network with:
Q80.
A wire of resistance R is bent to form a complete circle. Resistance between two diametrically opposite points:
Q81.
In a balanced Wheatstone bridge, P = 10 Ω, Q = 20 Ω and R = 30 Ω. The value of the unknown resistance S is:
Q82.
A wire of resistance R is stretched to double its length keeping the volume constant. Its new resistance is:
Q83.
Two cells, each of emf 2 V and internal resistance 1 Ω, are connected in series across a 2 Ω resistor. The current is:
Q84.
The power rating of a bulb is 100 W at 200 V. Its resistance is:
Q85.
In a metre bridge, the balance point is at 40 cm from one end. The ratio of the resistance in the left gap to that in the right gap is:
Q86.
A cell of emf 6 V and internal resistance 2 Ω delivers maximum power to an external resistor. That maximum power is:
Q87.
The drift velocity of electrons in a conductor is proportional to the current. If the current is doubled, the drift velocity:
Q88.
For a metallic conductor, as temperature increases, its resistance generally:
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