Tag: electric current, potential difference and resistance

Questions Related to electric current, potential difference and resistance

Drift velocity varies with the intensity of electric field as per the relation

physics electric current, potential difference and resistance drift velocity and mobility drift speed drift velocity & mobility

  1. ${v} _{d}\propto E$

  2. ${v} _{d}\propto \cfrac{1}{E}$

  3. ${v} _{d}=$ constant

  4. ${v} _{d}\propto {E}^{2}$

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Correct Option: A
Explanation:

Current , $I$ = $neAv _{d} $

Current density , $J$ = $\frac{I}{A}$ = $nev _{d} $
Also , current density $J$ is related to electric field $E$
by the relation 
$J = \sigma E$
Therefore , 
$nev _{d}$ = $J = \sigma E$
Hence , $v _{d}  \alpha E$ .

a current 10 ampere is maintained in a conductor of cross section of $ 10^{-4}m^2 $. if the electron density is $ 9 \times 10^{28} m^{-3} $ , what is the drift velocity of free electrons?

physics electric current, potential difference and resistance drift velocity and mobility drift speed drift velocity & mobility

  1. $ 6.9 \times 10^{-6} ms^{-1} $

  2. $ 6.9 \times 10^{-4} ms^{-1} $

  3. $ 6.9 \times 10^{5} ms^{-1} $

  4. none of thses

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Correct Option: A

The relaxation time $(t)$ is the:

physics electric current, potential difference and resistance drift velocity and mobility drift speed drift velocity & mobility

  1. Time taken by an electron to drift from one end of a conductor to the other.

  2. Time taken by an electron to travel unit distance through the conductor.

  3. The time between two successive collisions of a free electron with the atoms of the metal.

  4. Time for which a free electron is subjected to the electric field.

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Correct Option: C
Explanation:

Relaxation time is the average times between two successive collision between the free electrons and the atoms(kernel) of atoms .


It is denoted by $\tau$.

Answer-(C)

The drift velocity of free electrons in a conductor is $v$, when a current. $I$ is flowing in it if both the radius and current are doubled, then drift velocity will be.

physics electric current, potential difference and resistance drift velocity and mobility drift speed drift velocity & mobility

  1. $V/4$

  2. $V/2$

  3. $2V$

  4. $4V$

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Correct Option: B

Four persons are saying that they carry a negative charge of a certain value.which one of these statements given by the persons is incorrect?

physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

  1. I carry $1.90\times10^{-18}$ coulomb

  2. I carry $1.6\times10^{-18}$ coulomb

  3. I carry $1.92\times10^{-18}$ coulomb

  4. I carry $2.4\times10^{-16}$ coulomb

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Correct Option: A

What is the order of colour code for the insulation on the (a) live (b) neutral and (c) earth wire?

physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

  1. Brown, Blue and Green.

  2. Blue, green and brown.

  3. Green, blue and brown.

  4. Green,brown and blue.

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Correct Option: A
Explanation:

A 3 pin plug consists of three pins (hence the name). Each pin must be correctly connected to the three wires in the electrical cable. Each wire has its own specified color so as it can be easily identified.
The LIVE wire is RED OR BROWN. This is connected to a fuse on the live pin. The electric current uses the live wire as its route in.
The NEUTRAL wire is BLUE OR BLACK. This is the route the electric current takes when it exits an appliance; it is for this reason the neutral wire has a voltage close to zero.
The EARTH wire is GREEN OR  YELLOW and connected to the earth pin. This is used when the appliance has a metal casing to take any current away if the live wire comes in contact with the casing.

Where the switch is connected in a circuit ? 

physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

  1. in the ground wire.

  2. in the live wire

  3. in the neutral wire

  4. in live and neutral both.

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Correct Option: B
Explanation:

A switch opens or closes an electrical circuit. If the circuit is open, no electricity flows. If the circuit is closed, electricity flows through the circuit. 
Example:
A light switch is commonly used. When you turn the switch on, the circuit closes and electricity flows through the light. When you turn the switch off, the circuit is opened and the flow of electricity stops, making the light go out. 
In our homes, we receive supply of electric power through a main supply (mains), either supported through overhead electric poles or by underground cables.The live wire and neutral wire, coming from the electric pole, enter a box fitted just outside our house which has a main fuse.
The live wire is connected to the switch because, the live wire carries a voltage of 220 V and the passage of this voltage can be disabled by switching of the circuit.

The device used for producing current is called a _____.

physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

  1. Voltmeter

  2. Ammeter

  3. Galvanometer

  4. Generator

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Correct Option: D
Explanation:

In electricity generation A generator is a device which uses mechanical energy to produce electrical energy which flows in form of electric current in circuits. hence Generator can produce current.

Current in a circuit flows:

physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

  1. in direction from high potential to low potential

  2. in direction from low potential to high potential

  3. in direction of flow of electrons

  4. in any direction.

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Correct Option: A
Explanation:

Electric current flows from positive electrode of cell to negative electrode of cell, i.e., from high potential to low potential.

The conventional direction of flow of current is

physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

  1. negative terminal to positive terminal of the cell.

  2. positive terminal to negative terminal of the cell.

  3. opposite direction of electrons

  4. in direction of electrons.

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Correct Option: B,C
Explanation:

The current in the wire is due to the drifting of electrons inside a wire in a direction opposite to the flow of electrons. During their drifting they collide with their atoms vibrating about their mean position and lose some of kinetic energy to the vibrating atoms. 
The electrons are negatively charged particles and so, the electrons move towards the positively charged terminal from the negatively charged terminal.
Hence, the statement is true as the conventional direction of flow of current is from positive terminal to negative terminal of the cell.