Recent questions in Current Electricity

A high tension (HT) supply of say $6kv$ must have a very large internal resistance . Why ?

asked Jul 2, 2015 by meena.p

1 answer

A low voltage supply from which one needs high currents must have low internal resistance why ?

asked Jul 2, 2015 by meena.p

1 answer

Is Ohm's law universally applicable for all conducting elements? If not give examples of elements which do not obey ohm's law

asked Jul 2, 2015 by meena.p

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A steady current flow in a metallic conductor of non - uniform cross - section which of these quantities is constant along the conductor

asked Jul 2, 2015 by meena.p

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Explain why aluminium Wires are preferred for overhead power cables?

asked Jul 2, 2015 by meena.p

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Two wires of equal lengths , One of aluminium and the other of copper have the same resistance . Which of the two wires is lighter. $[\rho_A =2.63 \times 10^{-8} \Omega m, \rho_{cn}= 1.72 \times 10^{-8} \Omega -m$ . Relative density of $Al =2.7$ , Relative density of $Cu= 8.9 ]$

asked Jul 2, 2015 by meena.p

1 answer

A secondary cell after long use has an emt of $1.9\;V$ and a large internal resistance of $380 \Omega$ What maximum current can be drawn from the cell ?

asked Jul 1, 2015 by meena.p

1 answer

Six lead acid type of secondary cells each of emf $2.0V$ 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 ?

asked Jul 1, 2015 by meena.p

1 answer

What is the purpose of having a series resistor in the charging circuits?

asked Jul 1, 2015 by meena.p

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A storage battery of emf $8.0 V$ and internal resistance $0.5 \Omega$ is being changed by a $120\;V$ DC supply using a series resistor of $15. 5 \Omega$ What is the terminal voltage of the battery during changing ?

asked Jul 1, 2015 by meena.p

1 answer

The number of density of free electron in a copper conductor estimated at $8.5 \times 10^{20}m^{-3}$ . How long does an electron take a drift from one end of a wire $3.0 \; m$ long to its other end ? The area of cross - section of the wire is $2 \times 10^{-6}\;m^2$ and it is carrying of $3.0 \;A$

asked Jul 1, 2015 by meena.p

1 answer

In a potentiometer arrangement, a cell of emt $1.25\;V$ 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 $63.0\;cm$ , What is the emf of the second cell ?

asked Jul 1, 2015 by meena.p

1 answer

In a metre bridge , the balance point is found to be at $39.5\;cm$ from the end A, when the resistor Y is of $12.5 \;ohm$ . Determine the resistance of x. Why are the connections between resistors in a metre bridge made of thick copper ships ? What happens if the galvanometer and cell are interchanged at the balanced point of the bridge ? would the galvanometer show any current?

asked Jul 1, 2015 by meena.p

1 answer

Define the term electrical resistivity of a material. Write the S.I units. Derive an expression for the resistivity of a metal in terms of number density and mass of free electrons present in it .

asked Jul 1, 2015 by meena.p

1 answer

What is the Potential gradient? How is it measured? Explain

asked Jul 1, 2015 by meena.p

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If the length of the wire be doubled, What will be effect on the position of zero deflection in a potentio meter ? Explain

asked Jul 1, 2015 by meena.p

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Kirchhoff's first law obeys rule of conservation of charge Explain

asked Jun 30, 2015 by meena.p

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How does the fuse wire save the electrical installation?

asked Jun 30, 2015 by meena.p

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By what percentage will have the illumination of amp decrease if the current drops by $20\%$ ?

asked Jun 30, 2015 by meena.p

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A heating element using michrome connected to a $230\;V$ supply draws an initial current of $3.2 \;A$ Which settles after a few seconds to a steady value of $2.8 \;A$ . What is the steady temperature of the heating element if the room temperature is $27.0^{\circ}$ ? Temperature coefficient of resistance of michrome averaged over the temperature range involved is $1.70 \times 10^{-4 \circ}C^{-1}$

asked Jun 30, 2015 by meena.p

1 answer

A silver wire has a resistance of $2.1 \Omega$ at $27.5^{\circ}C$ and a resistance of $2.7\Omega$ at $100^{\circ}$ . Determine the temperature coefficient of resistivity of silver.

asked Jun 30, 2015 by meena.p

1 answer

At Room temperature $(27.0^{\circ})$ 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 resistance is $1.70 \times 10^{-4} .c^{-1}$

asked Jun 30, 2015 by meena.p

1 answer

A negligibly small current is passed through a wire of length $15\;cm$ and uniform cross section wire of length $6.0 \times 10^{-7}\;m^2$ and its resistance is measured to be $5.0 \Omega$ What is the resistivity of the material at the temperature of the experiment ?

asked Jun 30, 2015 by meena.p

1 answer

The storage battery of a car has an emt of $12\;V$ . If the interval resistance of a battery is $0.4 \Omega$ , What is the maximum current that can be drawn from the battery ?

asked Jun 30, 2015 by meena.p

1 answer

A current in a circuit having constant resistance is tripled. How does this affect the power dissipation ?

asked Jun 30, 2015 by meena.p

1 answer

What are the factor does the potential gradient of the potentiometer wire depend ?

asked Jun 30, 2015 by meena.p

1 answer

What is potential gradient? State its SI unit

asked Jun 30, 2015 by meena.p

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What are the two practical forms of wheat stone bridge?

asked Jun 30, 2015 by meena.p

1 answer

A resistance R is connected across a cell of emf e and internal resistance r. A potentio meter now measures the potential difference between the terminals of the cell as V. Write an expression for r in terms of e, V and R.

asked Jun 30, 2015 by meena.p

1 answer

Why is meter bridge also called a slide wire bridge ?

asked Jun 30, 2015 by meena.p

1 answer

A current of $1.0\;mA$ s flowing through a potentio meter wire of length $4\;m$ and of resistance $4 \Omega$ ,find the potential gradient of the potentio meter wire .

asked Jun 30, 2015 by meena.p

1 answer

When is the Wheatstones bridge most sensitive ?

asked Jun 30, 2015 by meena.p

1 answer

Resistance of a human body is of the order of $10 \;k \Omega$ . Why does one experience a strong wire of say $240\;V$ supply ?

asked Jun 30, 2015 by meena.p

1 answer

Why is the potential preferred over voltmeter for measuring e.m.f ?

asked Jun 30, 2015 by meena.p

1 answer

If P.d applied across a conductor is increased to $2V$ ,how will the drift velocity of the electrons change?

asked Jun 30, 2015 by meena.p

1 answer

If the length of a wire conductor is doubled by stretching it, keeping the p.d across it constant, by what factor does the drift speed of electrons charge ?

asked Jun 30, 2015 by meena.p

1 answer

What is the largest voltage you can safely put across a resistor marked $196 \Omega -1W$

asked Jun 30, 2015 by meena.p

1 answer

Two electric lamps A and B are marked. $220\;V- 100\;w$ and $220\;V-60\;W$ Out of the two which lamp has higher resistance ?

asked Jun 30, 2015 by meena.p

1 answer

Define electrical conductivity of a conductor and give in S.I unit .

asked Jun 30, 2015 by meena.p

1 answer

Two wires of equal length one of copper and of mangain have the same resistance which wire in thicker ?

asked Jun 30, 2015 by meena.p

1 answer

Name some elements which does not obey ohm's law

asked Jun 29, 2015 by meena.p

1 answer

What are the conditions required for making a conductor as a super conductor ?

asked Jun 29, 2015 by meena.p

1 answer

A wire of resistivity $\rho$ is stretched to three times its length . What will be the new resistivity ?

asked Jun 29, 2015 by meena.p

1 answer

What is the conductance of a wire of resistance $2\;m \sigma$ ?

asked Jun 29, 2015 by meena.p

1 answer

Give the relation between drift velocity and electric field

asked Jun 29, 2015 by meena.p

1 answer

Explain why bending a wire does not affect its electrical resistance ?

asked Jun 29, 2015 by meena.p

2 answers

How will you represent a resistance of $3700 \Omega \pm 10\%$ by colour code?

asked Jun 29, 2015 by meena.p

1 answer

A carbon resistance is marked in red, green, and orange bands . What is the approximate resistance of the resistor ?

asked Jun 29, 2015 by meena.p

1 answer

There resistors $1 \Omega, 2 \Omega$ and $3 \Omega$ are combined in series . What is the total resistance of the combination ? b) If the combination is connected to a battery of emf $12\;V$ and negligible internal resistance , Obtain the potential drop across each resistors?

asked Jun 29, 2015 by meena.p

1 answer

A battery of emf $10\;v$ and internal resistance $3 \Omega$ is connected to a resistor . If the current in the circuit is $0.5\;A$ , What is the resistance of the resistor ? What is the resistance of the resistor ? What is the terminal voltage of the battery when the circuit is closed ?

asked Jun 29, 2015 by meena.p

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