Recent questions tagged ch-3

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

asked Jun 30, 2015 by meena.p

1 answer

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

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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

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

asked Jun 30, 2015 by meena.p

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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

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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

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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

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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

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

asked Jun 30, 2015 by meena.p

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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

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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

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

asked Jun 30, 2015 by meena.p

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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

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

asked Jun 30, 2015 by meena.p

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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

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Name some elements which does not obey ohm's law

asked Jun 29, 2015 by meena.p

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

asked Jun 29, 2015 by meena.p

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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

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

asked Jun 29, 2015 by meena.p

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Give the relation between drift velocity and electric field

asked Jun 29, 2015 by meena.p

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$V-I$ graph for a metallic wire at two different temperatures $T_1$ and $T_2$ are shown in the figure. Which of the two temperature is higher and why ?

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

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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

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What are the dimensions of electrical conductivity ?

asked Jun 29, 2015 by meena.p

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A wire of resistance $4R$ is bent in the form of a circle. What is the effective resistance between the ends of diameter ?

asked Jun 29, 2015 by meena.p

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a)Three resistor $2 \Omega,4 \Omega$ and $ 5\;\Omega$ are combined in parallel. What is the total resistance of the combination ? b) If the combination is connected to a battery emf $20\;V$ and negligible internal resistance determine the current through each resistor, and the total current drawn from the battery

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

1 answer

The storage battery of a can an ems of $ 12V$ .If the internal resistance of the battery is $ 0.4 \Omega$ What is the maximum current that can be drawn from the battery ?

asked Jun 29, 2015 by meena.p

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The resistivity of a typical insulator (eg: amber) is greater that of a metal by a factor of the order of $10^{22} /10^{23}$

asked Jun 29, 2015 by meena.p

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Alloys usually have lower/higher temperature is nearly independent of / increases rapidy with increase of temperature

asked Jun 29, 2015 by meena.p

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Alloys of metals have greater / lesser resistivity than that of their constituent metal?

asked Jun 29, 2015 by meena.p

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What conclusion can you draw from the following observation on a resistor made of allong magnanin ?Choose the correct alternative?

asked Jun 29, 2015 by meena.p

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When electrons drift in a metal from lower to higher potential , does it means that all the free electrons of the metal are moving in the same direction ?

asked Jun 29, 2015 by meena.p

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If the electron drift speed is so small , and the electron's charge is small , how can we still obtain large amount of current in a conductor ?

asked Jun 29, 2015 by meena.p

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The electron drift arises due to the force experience by electrons in the electric field inside the conductor . But force should cause acceleration . When then do the electrons acquire a steady average drift speed ?

asked Jun 29, 2015 by meena.p

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The electron drift speed is estimated to be only a few $mms^{-1} $ for currents in the range of a few amperes. How then is current established almost instant a circuit is closed.

asked Jun 29, 2015 by meena.p

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Given the resistance of $1 \Omega, 2 \Omega,3 \Omega$ how will you combine thus to get , an equivalent resistance of $(i) \large\frac{11}{3}$$\Omega \qquad (ii) \large\frac{6}{11}$$\Omega \qquad (iii) \large\frac{11}{5}$$\Omega \qquad (iv) 6 \Omega? $

asked Jun 29, 2015 by meena.p

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Given n resistors each of resistance R, how will you combine them to get, (i) maximum effective resistance (ii) minimum effective resistance ? What is the ratio of the maximum to minimum resistance

asked Jun 29, 2015 by meena.p

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A high tension (HT) supply of say $6\;KV$ must have a very large internal resistance why ?

asked Jun 29, 2015 by meena.p

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Is Ohm's law universally applicable for all conducting element ? If not give example of elements which do not obey Ohm's law.

asked Jun 29, 2015 by meena.p

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

asked Jun 29, 2015 by meena.p

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