Answer the following questions:
A low voltage supply from which one needs high currents must have very low internal resistance. Why?
A low voltage supply from which one needs high currents must have very low internal resistance. Why?
Question types
Current Electricity question types
602 questions across 6 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.
602
Questions
6
Question groups
5
Question types
01
2 Marks Questions
93 Q→023 Marks Question
102 Q→031 Marks Question
57 Q→04M.C.Q (1 Marks)
227 Q→05Assertion (A) & Reason (B) MCQ
20 Q→065 Marks Questions
103 Q→Sample Questions
Current Electricity questions
One sample from each question group in this chapter. Select any group above to see the full set with answer keys.
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At room temperature (27.0°C) the resistance of a heating element is $100\ \Omega.$ What is the temperature of the element if the resistance is found to be $117\ \Omega,$ given that the temperature coefficient of the material of the resistor is $1.70\times10^{-4}\ ^\circ\text{C}^{-1}.$
View full solution →A silver wire has a resistance of $2.1\ \Omega\ \text{at}\ 27.5^\circ\text{C},$ and a resistance of $2.7\ \Omega\ \text{at}\ 100^\circ\text{C}.$ Determine the temperature coefficient of resistivity of silver.
View full solution →What conclusion can you draw from the following observations on a resistor made of alloy manganin?
| Current A | Voltage V | Current A | Voltage V |
| 0.2 0.4 0.6 0.8 1.0 2.0 | 3.94 7.87 11.8 15.7 19.7 39.4 | 3.0 4.0 5.0 6.0 7.0 8.0 | 59.2 78.8 98.6 118.5 138.2 158.0 |
In a potentiometer arrangement, a cell of emf 1.25 V gives a balance point at 35.0 cm length of the wire. If the cell is replaced by another cell and the balance point shifts to 63.0 cm, what is the emf of the second cell?
A resistance of R draws current from a potentiometer. The potentiometer wire, AB, has a total resistance of Ro. A voltage V is supplied to the potentiometer. Derive an expression for the voltage across R when the sliding contact is in the middle of potentiometer wire.
- Three resistors $2\ \Omega,\ 4\ \Omega\ \text{and}\ 5\ \Omega$ are combined in parallel. What is the total resistance of the combination?
- If the combination is connected to a battery of emf 20 V and negligible internal resistance, determine the current through each resistor, and the total current drawn from the battery.
- In a metre bridge [Fig. 3.27], the balance point is found to be at 39.5 cm from the end A, when the resistor Y is of $12.5\ \Omega.$ Determine the resistance of X. Why are the connections between resistors in a Wheatstone or meter bridge made of thick copper strips?
- Determine the balance point of the bridge above if X and Y are interchanged.
- What happens if the galvanometer and cell are interchanged at the balance point of the bridge? Would the galvanometer show any current?
- Six lead-acid type of secondary cells each of emf 2.0 V and internal resistance $0.015\Omega$ are joined in series to provide a supply to a resistance of $8.5\ \Omega.$ What are the current drawn from the supply and its terminal voltage?
- A secondary cell after long use has an emf of 1.9 V and a large internal resistance of $380\ \Omega$ What maximum current can be drawn from the cell? Could the cell drive the starting motor of a car?
Determine the current drawn from a 12 V supply with internal resistance $0.5\ \Omega$ by the infinite network shown in Fig. Each resistor has $1\ \Omega$ resistance.
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Answer the following questions:
Is Ohm’s law universally applicable for all conducting elements? If not, give examples of elements which do not obey Ohm’s law.
Is Ohm’s law universally applicable for all conducting elements? If not, give examples of elements which do not obey Ohm’s law.
Choose the correct alternative:
The resistivity of a typical insulator (e.g., amber) is greater than that of a metal by a factor of the order of (1022/103).
The resistivity of a typical insulator (e.g., amber) is greater than that of a metal by a factor of the order of (1022/103).
Choose the correct alternative:
Alloys of metals usually have (greater/ less) resistivity than that of their constituent metals.
Alloys of metals usually have (greater/ less) resistivity than that of their constituent metals.
Choose the correct alternative:
Alloys usually have much (lower/ higher) temperature coefficients of resistance than pure metals.
Alloys usually have much (lower/ higher) temperature coefficients of resistance than pure metals.
Choose the correct alternative:
The resistivity of the alloy manganin is nearly independent of/ increases rapidly with increase of temperature.
The resistivity of the alloy manganin is nearly independent of/ increases rapidly with increase of temperature.
The conductivity of a metal decreases with the increase in temperature on account of:
- ADecrease in number density of electrons.
- BDecrease in resistivity.
- CDecrease in relaxation time.
- DIncrease in mean free path.
Kirchhoff ’s first rule at a junction in an electrical network, deals with conservation of:
- AEnergy.
- BCharge.
- CMomentum.
- DBoth energy and charge.
A potentiometer can measure emf of a cell because:
- AThe sensitivity of potentiometer is large.
- BNo current is drawn from the cell at balance.
- CNo current flows in the wire of potentiometer at balance.
- DInternal resistance of cell is neglected.
Two resistors R1 and R2 of $4\Omega$ and $6\Omega$ are connected in parallel across a battery. The ratio of power dissipated in them, P1 : P2 will be:
- A4 : 9
- B3 : 2
- C9 : 4
- D2 : 3
Appliances based on heating effect of current work on:
- AOnly a.c.
- BOnly d.c.
- CBoth a.c. and d.c.
- DNone of these.
For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Reason: On increasing the temperature, the resistance of metals and alloys increases.
- Both A and R are true, and R is the correct explanation of A.
- Both A and R are true, but R is not the correct explanation of A.
- A is true, but R is false.
- A is false, and R is also false.
Reason: On increasing the temperature, the resistance of metals and alloys increases.
For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Reason: Insulator have no free charge carrier.
- Both A and R are true, and R is the correct explanation of A.
- Both A and R are true, but R is not the correct explanation of A.
- A is true, but R is false.
- A is false, and R is also false.
Reason: Insulator have no free charge carrier.
For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Reason: The current carrying wire attracts the man towards it.
- Both A and R are true, and R is the correct explanation of A.
- Both A and R are true, but R is not the correct explanation of A.
- A is true, but R is false.
- A is false, and R is also false.
Reason: The current carrying wire attracts the man towards it.
For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Reason: Fuse is used for small current flow only.
- Both A and R are true, and R is the correct explanation of A.
- Both A and R are true, but R is not the correct explanation of A.
- A is true, but R is false.
- A is false, and R is also false.
Reason: Fuse is used for small current flow only.
For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Reason: Kilo-watt hour is the unit of electric power.
- Both A and R are true, and R is the correct explanation of A.
- Both A and R are true, but R is not the correct explanation of A.
- A is true, but R is false.
- A is false, and R is also false.
Reason: Kilo-watt hour is the unit of electric power.
Determine the current in each branch of the network shown in Fig.:
Two wires of equal length, one of aluminium and the other of copper have the same resistance. Which of the two wires is lighter? Hence explain why aluminium wires are preferred for overhead power cables.
$(\rho_{\text{A}1}=2.63\times10^{-8}\Omega\ \text{m,}\ \text{Relative density of Al}=2.7,\ \text{of Cu}=8.9)$
View full solution →$(\rho_{\text{A}1}=2.63\times10^{-8}\Omega\ \text{m,}\ \text{Relative density of Al}=2.7,\ \text{of Cu}=8.9)$
Given the resistances of $1\ \Omega,\ 2\ \Omega,\ 3\ \Omega,$ how will be combine them to get an equivalent resistance of,
View full solution →- $(11/3)\ \Omega$
- $(11/5)\ \Omega$
- $6\ \Omega$
- $(6/11)\ \Omega?$
Figure shows a potentiometer with a cell of 2.0 V and internal resistance $0.04\ \Omega$ maintaining a potential drop across the resistor wire AB. A standard cell which maintains a constant emf of 1.02 V (for very moderate currents upto a few mA) gives a balance point at 67.3 cm length of the wire. To ensure very low currents drawn from the standard cell, a very high resistance of $600\ \text{k}\Omega$ is put in series with it, which is shorted close to the balance point. The standard cell is then replaced by a cell of unknown emf $\varepsilon$ and the balance point found similarly, turns out to be at 82.3 cm length of the wire.
View full solution →- What is the value $\varepsilon?$
- What purpose does the high resistance of $600\ \text{k}\Omega$ have?
- Is the balance point affected by this high resistance?
- Is the balance point affected by the internal resistance of the driver cell?
- Would the method work in the above situation if the driver cell of the potentiometer had an emf of 1.0 V instead of 2.0 V?
- Would the circuit work well for determining an extremely small emf, say of the order of a few mV (such as the typical emf of a thermo-couple)? If not, how will you modify the circuit?
Determine the equivalent resistance of networks shown in Fig.
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