Tag: electric current, potential difference and resistance

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Questions Related to electric current, potential difference and resistance

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

 If 'n' electrons flow through a cross-section of a conductor in time t and charge on an electron is 'e', then the current in the conductor would be :

  1. $\displaystyle \frac{ne}{t}$

  2. $\displaystyle \frac{ne^2}{t}$

  3. $\displaystyle \frac{e}{t}$

  4. $\displaystyle \frac{n}{et}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Consider a conductor of length of $L$ and cross sectional area $A$. 

When an electric field $E$ is applied across it, the electrons are drifted opposite to the applied field. 
Volume of a conductor $= LA =1$ in this case. 
Let $n$ be the number of free electrons per unit volume of conductor.
Total charge on all the electrons in the conductor $= nLAe$ 
where, $e$ is the charge of each electron.

$\Rightarrow  q = nLAe = neAL$ 

But current, $I=\dfrac { q }{ t } =\dfrac { neAL }{ t } =\dfrac { ne }{ t } \quad as\quad AL=1$

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

Sulphate ions move toward

  1. copper electrode

  2. battery

  3. electrolyte

  4. zinc electrode
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Sulphate ions move toward zinc electrode.
Oxidation half reaction occurs at anode.
$\displaystyle Zn \rightarrow Zn^{2+} +2e^-$
Positively charged Zn(II) ions enter anode solution. To maintain electrical neutrality, sulphate ions move toward zinc electrode.

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

In a cell, by convention, charge is taken to be flowing from :

  1. positive electrode to negative electrode

  2. negative electrode to positive electrode

  3. both A and B

  4. none of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Conventionally, movement (flow) of positive charge is considered and because, unlike charge repel each other, positive charge moves from positive electrode to negative electrode inside the cell. Hence option A is correct.

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

Two conductors $A$ and $B$ are joined by a copper wire.  If $A$ is positively charged and $B$ is uncharged, the direction of flow of electrons is 

  1. $B$ to $A$

  2. $A$ to $B$

  3. no flow

  4. none of these.
Reveal answer Fill a bubble to check yourself
A Correct answer
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 conductor A.
Hence, the direction of the flow of electrons in the copper wire is from B to A.

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

The chemical reaction due to passage of electric current depends on:

  1. electrodes.

  2. magnitude of current.

  3. density of liquid.

  4. all of the above.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The chemical reaction due to passage of electric current depends on electrodes.
For example, during electrolysis of aqueous copper sulphate solution using platinum electrodes will give oxygen gas at anode.
On the other hand, during electrolysis of aqueous copper sulphate solution using copper electrodes will oxide Cu to Cu(II) ions at anode.

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

Conventionally, the direction of the current is taken as

  1. the direction of flow to negative charge

  2. the direction of flow of atoms

  3. the direction of flow of molecules

  4. the direction of flow of positive charge
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Conventionally the direction of flow of current is taken to be the direction of flow of positive charges.


In wire, electrons possessing negative charges flow and positive charged kernel are at rest.
And, hence the direction of flow of current is opposite to the direction of flow of electrons in wires.

Answer-(D)

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

It is possible to measure the passage of $50$ electrons per second with a certain sensitive device. This corresponds to a current of :

  1. $8 \times 10^{-18} A$

  2. $1.6 \times 10^{-20} A$

  3. $8 \times 10^{-20} A$

  4. $1.6 \times 10^{-19} A$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation


Let number of electrons per second be n.
Given,
$e = 1.6 \times 10^{-19} C$ ,  $n =50 $
The current is defined as rate of flow of charge,
$I = \dfrac{q}{t} $ 
Hence,
$I = n \times e $

Substituting values,
$I = 50 \times 1.6\times 10^{-19} = 8 \times 10^{-18} A $

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

Conventionally, the direction of the current is taken as the direction of flow

  1. to negative charge

  2. the direction of flow of atoms

  3. of molecules

  4. of positive charge
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Conventional Current assumes that current flows out of the positive terminal, through the circuit and goes into the negative terminal of the source.

it's not absolute direction of current it is just conventional which is used to describe the direction of current in electrical circuits.

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

A particle of mass $2\ g$ and charge $1\ \mu C$ is held at a distance of $1\ m$ from a fixed charge of $1\ mC.$ If the particle of released it will be repelled. Speed  of the particle when it is at a distance of $10\ m$ from the fixed charge is

  1. $100\ m/s$

  2. $90\ m/s$

  3. $60\ m/s$

  4. $45\ m/s$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

energy of the whole system will be conserved .


so the change in the potential energy of the system will be converted into the kinetic energy of the particle 

$K(q _{1}*q _{2})/(1/r _{1}-1/r _{2})$  $=$  $(m*v^{2})/2$


substituting the values will give 

$V = 90$ $m/s$

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

On a bulb is written 220 volt and 60 watt. Find out the resistance of the bulb and the value of the current flowing through it:

  1. $806.66 ohm\ and\ 0.27 ampere$

  2. $500 ohm \ and\ 2 amphere$

  3. $200 ohm  \ and\ 4 ampere$

  4. $100 ohm \ and\ 1 ampere$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$R=\dfrac {V^2}{P}=\dfrac {(60^2)}{220}$
$=806.66 \Omega$
$I=\dfrac {P}{V}$
$=\dfrac {6-0}{220}=0.27$