Tag: electric potential and potential difference

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

Electric current is due to drift of electrons in

  1. Metallic conductors

  2. Semiconductors

  3. Both (a) and (b) above

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

Answer is A.
When an electric field is applied across the metallic conductors the randomly moving electrons are subjected to electrical forces along the direction of the field. Due to this field, the electrons do not give up their randomness of motion, but they will be shifting towards higher potential. That means the electrons will drift towards higher potential along with their random motions. 
In semiconductors, in addition to electrons, the travelling vacancies in the valence-band electron population (called 'holes'), act as mobile positive charges and are treated as charge carriers. Electrons and holes are the charge carriers in semiconductors.
Hence, electric current is due to drift of electrons in metallic conductors.

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

State whether given statement is True or False
Conventional current always flows from a body having high electron density to body having to body having low electron density.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Conventional Current assumes that current flows out of the positive terminal, through the circuit and into the negative terminal of the source. This was the convention chosen during the discovery of electricity.
Not from high electron density to low electron density.

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

In case of electronic current the charge flows from negatively charged body to the positively charged body. The body which is at higher potential is 

  1. <span>negatively charged body</span>

  2. <span>positively charged body</span>

  3. <span>both are at same potential</span>

  4. <span>none of these</span>
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

By convention a positively charged body is always at a higher potential as compared to negatively charged body . If positive charges like protons or positive ions are free to move they would move from higher potential point to lower potential point.

In case of electronic current the charge flows from negatively charged body to the positively charged body. The body which is at higher potential is positively charged body

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

A big hallow metal sphere $A$ is charged to $100$ volts and another smaller hollow sphere $B$ is charged to $50$ volts. If B is put inside $A$ and joined with a metallic wire, then the direction of charge flow:-

  1. is from $A$ to $B$

  2. is from $B$ to $A$

  3. to charge flows

  4. depends on the radii of spheres
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Charge flows from a higher potential to a lower potential. Since sphere A is at 100V and sphere B is at 50V, charge will flow from A to B until they reach the same potential.

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

A DC current flows through a vertical wire in the downward direction. For an observer looking at the wire, the direction of magnetic field at a point between him and the wire is:

  1. Upward

  2. To the right

  3. To the left

  4. Downward
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Using the right-hand grip rule for a downward current, the magnetic field lines form circles around the wire. For an observer looking at the wire, the field at a point between them and the wire points to the right.

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

An aluminium (Al) rod with area of cross-section $4\times 10^{-6}m^2$ has a current of 5A. Flowing through it. Find the drift velocity of electron in the rod. Density of $Al=2.7\times 10^3kgm^{-3}$ and atomic wt.=27. Assume that each Al atom provides one electron.

  1. $8.6\times 10^{-4}ms^{-1}$

  2. $6.2\times 10^{-4}ms^{-1}$

  3. $1.2\times 10^{-4}ms^{-1}$

  4. $3.8\times 10^{-3}ms^{-1}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Drift velocity v_d = I / (n*A*e). The number density n = (density * Avogadro's number) / atomic weight. Calculating n for Aluminum and substituting into the formula yields approximately 1.2*10^-4 m/s.

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

When you flip a switch to turn on a light, the delay before the light turns on is determined by :

  1. The speed of the electric fields moving in the wire.

  2. the drift speed of the electrons in the wire.

  3. the number of electron collisions per second in the wire.

  4. none of these, since the light comes instantly.
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

A vertical wire carries a current in upward direction. If an electron beam sent horizontally towards the wire, then it will deflected.

  1. vertically downwards and perpendicular to the plane of the paper

  2. vertically upwards and perpendicular to the plane of the paper

  3. In the plane of the paper

  4. No deflection
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Using right-hand rule for upward current: magnetic field circles the wire. For a horizontally directed electron beam approaching the wire, force F = -e(v × B). The force direction depends on whether beam approaches from left or right of wire - not specified. Assuming beam approaches from left side of wire (viewer's perspective), it deflects vertically downward perpendicular to paper plane.