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

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.

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

If the strenath of the majestic field produced $10 \mathrm { cm }$ away from a infinitely long straight conductor is $10 ^ { - 5 } \text { weber/m } ^ { 2 }$ the value of the current flowing in the conductor will be:

  1. $5\ ampere$

  2. $10\ ampere$

  3. $500\ ampere$

  4. $1000\ ampere$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The magnetic field B of an infinite wire is B = (mu_0 * I) / (2 * pi * r). Rearranging for I: I = (B * 2 * pi * r) / mu_0. Given B = 10^-5, r = 0.1m, and mu_0 = 4*pi*10^-7, I = (10^-5 * 2 * pi * 0.1) / (4 * pi * 10^-7) = 5 A.

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

If current density in a conducting wire is proportional to the distance r from the axis of the conductor, then find magnetic field at the position r<R , where R is the radius of cross section of the conductor.('i'is the current in conducting wire)

  1. $ \frac { \mu _0ir^2 }{2 \pi R^3} $

  2. $ \frac { \mu _0ir^2 }{4 \pi R^3} $

  3. $ \frac { \mu _0ir^2 }{2 \pi R^2} $

  4. $ \frac { \mu _0ir^2 }{2 \pi R^4} $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Using Ampere's Law, integral(B dl) = mu_0 * I_enclosed. If current density J = kr, then I_enclosed = integral(J * 2*pi*r dr) from 0 to r. Solving this and relating k to total current I gives the field B = (mu_0 * I * r^2) / (2 * pi * R^3).

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

Electric current flows from positive terminal of battery to negative terminal.

  1. True

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

By convention, the direction of conventional electric current is defined as the flow of positive charge, which is from the positive terminal to the negative terminal.

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

Two conducting parallel plates areseparated by a distance of 0.001$\mathrm { m } . \mathrm { A } 9 \mathrm { V }$battery is connected across the plates.Find out the electric field between the plates? 

  1. 9000$\mathrm { V } / \mathrm { m }$

  2. 900$\mathrm { Vim }$

  3. 9$\mathrm { V } / \mathrm { m }$

  4. <span>.9$\mathrm { V } / \mathrm { m }$</span>
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The electric field E between parallel plates is given by E = V / d. Given V = 9 V and d = 0.001 m, E = 9 / 0.001 = 9000 V/m.

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

The number of free electrons passing through the filament of an electric lamp is one hour when the current through the filament is 0.32 A will be 

  1. $3\times { 10 }^{ 22 }$

  2. $2\times { 10 }^{ 26 }$

  3. $7.2\times { 10 }^{ 19 }$

  4. $7.2\times { 10 }^{ 21 }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Total charge Q = I * t = 0.32 A * 3600 s = 1152 C. Number of electrons n = Q / e = 1152 / 1.6*10^-19 = 7.2*10^21.

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

The current density $ \bar { j }  $ at cross-sectional area $ \bar { A } = (2 \hat {i} + 4 \hat {j} )mm^{-2}$  is $(2 \hat {j} + 2 \hat {k} ) A m^{-2} $ The current following through the cross-sectional area is

  1. $ 12 \mu A $

  2. $ 8 \mu A $

  3. $ 4 \mu A $

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

Current I = J dot A. Given J = (2j + 2k) A/m^2 and A = (2i + 4j) mm^2 = (2i + 4j) * 10^-6 m^2. The dot product is (0*2 + 2*4 + 2*0) * 10^-6 = 8 * 10^-6 A = 8 microA.

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

A flow of $10^{12}$ electrons per minute in a conducting wire constitutes a current of 

  1. $1.6 \times 10^{-7}\, A$

  2. $1.6 \times 10^{-8}\, A$

  3. $2.67 \times 10^{-9}\, A$

  4. `$2.67 \times 10^{-10}\, A$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Current I = q / t. Total charge q = 10^12 * 1.6*10^-19 = 1.6*10^-7 C. Time t = 60 s. I = 1.6*10^-7 / 60 = 2.67*10^-9 A.