Tag: electromagnetic forces

Questions Related to electromagnetic forces

The magnitude of current is ........ the magnitude of magnetic field

physics electromagnetic forces magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

  1. Inversely proportional to

  2. Directly proportional to

  3. Same as

  4. None of the above

Show answer
Correct Option: B
Explanation:

In his experiment Oersted observed that as the current in the wire increased, the deflection of the needle also increased, indicating that they are directly proportional.

Which of the following observations are true for Hans Oersteds experiment?
a. When current passes through the wire the compass needle comes to rest in a direction along the Earths magnetic field.
b. When placed just above the wire, North Pole of the compass needle deflects towards the east when current is passes from A to B.
c. When placed just below the wire, North Pole of the compass needle deflects towards the east when current is passes from B to A i.e. on reversing the direction of current

physics electromagnetic forces magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

  1. a and c

  2. a and b

  3. b and c

  4. All of the above

Show answer
Correct Option: C
Explanation:

Oersted conducted an experiment to study the magnetic effect of electric current. In this experiment he observed the deflections of a compass needle placed in close proximity of an electric wire carrying current. He observed that in the absence of current the needle came to rest in Earths North-south direction under the influence of Earths magnetic field. However, when the needle was kept below the wire and current was passed from A to B the north pole of the needle deflected towards the west and on reversing the direction of the current from B to A, it deflected towards the east. Similarly, when the needle was kept above the wire and current was passed from A to B the north pole of the needle deflected towards the east and on reversing the direction of the current from B to A, it deflected towards the west. This indicates that the direction of the magnetic field depends on the direction of current.

When current passes through the circuit a compass needle rests in which direction (with respect to the Earth)?

physics electromagnetic forces magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

  1. South-north

  2. North-south

  3. East-west

  4. West-east

Show answer
Correct Option: A
Explanation:

The earth acts like a huge magnet. Thus in the absence of electric current a compass needle always comes to rest in Earths North-south direction. However, when current passes through the circuit the needle comes to rests in the direction opposite to the magnetic field of Earth i.e. South-North direction.

State whether True or False :

If electric current is passed through metal body then it behaves as magnet.

physics electromagnetic forces magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

  1. True

  2. False

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Correct Option: A
Explanation:

If electric current is passed through metal body then it behaves as magnet. passing an electric current through iron does not produce a magnet. But if you pass a direct current through a coil wound around the piece of iron, you will magnetize it. Passing a direct electric current through the same coil with no iron inside the coil will still produce a magnetic field that behaves just like a magnet. Similarly, passing a direct current through a coil around a piece of Bismuth will create the same magnetic field which behaves just like a magnet.

Who first discovered the relationship between electricity and magnetism?

physics electromagnetic forces magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

  1. Faraday

  2. Newton

  3. Maxwell

  4. Oersted

Show answer
Correct Option: D
Explanation:

Oersted discovered the relationship between electricity and magnetism.

Chose the correct statement from the following:

physics electromagnetic forces magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

  1. Electric current is a scalar quantity

  2. Charge carries in metals are ions

  3. The area of current- time graph gives charge

  4. A charge in motion produces both electric and magnetic field

Show answer
Correct Option: A,C,D
Explanation:
$(i)$ Option- $A$ is correct, since current has no directional attribute to it, it is a scalar quantity.
$(ii)$ Option- $B$ is correct, Charge carries in metal are free electrons whereas in electrolytic solution they are ions
$(iii)$ Option- $C$ is correct because $i=\dfrac{da}{dt}\Rightarrow =i dt \Rightarrow a=\displaystyle \int{i. dt}$
$\displaystyle \int{i. dt}$ is the area under current-time graph
$(iv)$ Option- $D$ is correct, charge in motion produces current which in term produces magnetic field.

Two long parallel wires A and B separated by a distance d, carry currents $i _1$ and $i _2$ respectively in the same direction. Write the following steps in a sequential order to find the magnitude of the resultant magnetic field at a point 'P', which is between the wires and is a distance '$x$' from the wire A.
(All the physical quantities are measured in SI units)
(a) Note the given values of $i _1, i _2$, $d$ and $x$.
(b) Write the formula to find the magnetic field due to a long straight current carrying wire i.e. $\displaystyle B=\frac{\mu _0 i}{2 \pi r}$
(c) Find the directions of the magnetic field at 'P' due to two wires A and B, using right hand thumb rule.
(d) Determine the magnetic field at P due to wire A, using $B _1 \displaystyle = \frac{\mu _0 i _1}{2 \pi x}$
(e) If the directions of magnetic field are same, then the resultant magnitude is equal to the sum of $B _1$ and $B _2$.
(f) Determine the magnetic field $B _2$ due to wire B at point P, ie. $B _2 = \displaystyle \frac{\mu _o i _2}{2 \pi (d-x)}$
(g) If the directions of magnetic fields are opposite to each other, then the resultant magnitude is equal to the difference of $B _1$ and $B _2$.

physics electromagnetic forces magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

  1. $d f c e g b a$

  2. $c d f e g b a$

  3. $a c b d f e g$

  4. $a b d f c e g$

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Correct Option: D

Consider a region where both uniform electric and magnetic fields E and B are present both along the z-axis. A positively charged particle of charge and mass is released from the origin with an initial velocity ${{\text{V}} _e}\hat i$. Which of the following option(s) are correct?

physics electromagnetic forces magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

  1. (A)The y coordinate of the particle at time ${\text{t}} = \frac{{\pi {\text{M}}}}{{{\text{qB}}}}{\text{ is}}\frac{{ - 2{\text{mv}}}}{{{\text{qB}}}}$

  2. (B)The distance between two consecutive point on the z-axis where the particle touches the Z-axis is an odd multiple of a constant distance.

  3. (C)The distance between two consecutive point on the z-axis where the particle touches the Z-axis is an even multiple of a constant distance.

  4. (D)The time after which the particle touches the z-axis is $\frac{{2\pi {\text{m}}}}{{{\text{qB}}}}$

Show answer
Correct Option: A

A thermistor:

physics electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

  1. Is a thermally sensitive resistor

  2. Is made of a semiconductor

  3. Has negative temperature coefficient of resistance

  4. All the above

Show answer
Correct Option: D
Explanation:
A thermistor is a type of resistor whose resistance depends on temperature, more than in standard resistor. The word is a combination of thermal and resistor. They are widely used as inrush current limiters, temperature sensors, self -resetting overcurrent protectors, and self-regulating heating elements.
It is made up of semiconductors and has a negative temperature coefficient of resistance.

Thermistor has a resistance of ________

physics electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

  1. 250 to 500 k ohms

  2. 50 to 10 k ohms

  3. 1 to 1 k ohms

  4. 100 to 100 k ohms

Show answer
Correct Option: D
Explanation:

Thermistor has a resistance range of 100 to 100 k. Thermistor consists of a mixture of metallic oxides of manganese, nickel, cobalt, copper, iron and uranium.