# ELECTROMAGNETISM

Unit 15

Q.1. What does one mean by electromagnetism? What are its uses?

Ans. The study of magnetic effects of current is thought as electromagnetism.

Uses

The use of electromagnetism in several fields of science and technology is incredibly wide. Motors and electrical meters are supported the result of magnetism made by the electrical current in wires.

Generators manufacture current thanks to the movement of wires close to terribly giant magnets

Q.2. Demonstrate by AN experiment that a magnetic flux is made around a straight current-carrying conductors,

Ans. Take a straight conductor wire and pass it vertically through a cardboard (Fig.15.1-a). currently connect the 2 ends of the conductor wire with the terminals of the battery so current flows through the circuit within the clockwise direction. The lines of force of the magnetic flux made round the wire would be within the sort of concentric circles. If we have a tendency to place a compass needle at totally different points within the region of magnetic flux, it’ll align on the direction of magnetic flux. Also, if we have a tendency to sprinkle some iron filings on the cardboard round the wire, they’ll align themselves in concentric circles within the clockwise direction

Current-carrying conductor

Lines of

Magnetic

Field

Current-carrying conductor

Lines of

Magnetic

Field

Compass Needle

Paper

Electromagnetic Field (Clockwise)

Electromagnetic Field (Anticlockwise)

If we have a tendency to reverse the direction of the present by reversing the terminals of the battery, the compass needle conjointly reverse its direction. currently the magnetic flux lines can align within the anticlockwise direction (Fig.15.1-b). The magnetic flux made is stronger close to the centre of the current-carrying conductor and weaker farther method from it.

Q.3. State and justify the rule by that the direction of the lines of force of the magnetic flux around a current-carrying conductor are often determined.

Ans. The direction of the magnetic fields or lines of force is ruled by the direction of the present flowing through the conductor. an easy methodology of finding the direction of magnetic flux round the conductor is that the manus Grip Rule. it’s declared as:

Grasp a wire together with your manus such your thumb pointed within the direction of the standard (positive) current. Then curling fingers of your hand can purpose within the direction of the magnetic flux.

Q.4. what’s solenoid? justify that a current-carrying coil includes a north and pole and is itself a magnet.

Ans. SOLENOID

A long coil of wire consisting of the many loops is  Head a coil.

The filed from every loop during a coil adds to the fields of the opposite loops and creates bigger total intensity level. current within the coil of wire produces magnetic flux that is comparable to the magnetic flux of a static magnet. once this current-carrying coil is brought nearer to a suspended magnet, one finish of the coil repels the pole of the magnet. Thus, the current-carrying coil includes a north and a pole and is itself a magnet.

Fig.15.3. magnetic flux thanks to a coil

Q.5 what’s AN electromagnet?

Ans. magnet

The type of temporary magnet, that is formed once current flows through a coil is termed AN magnet. .

Q.6. however the direction of the sphere made by a coil thanks to the flow of typical current are often found?

Ans. The direction of the sphere made by a coil thanks to the flow of typical current are often found with the assistance of manus Grip Rule.

It is declared as:

Conventional * current flow

If we have a tendency to grip the Coil With Our right f

Fig.15.4: manus grip rule for a coil

hand by curling our fingers in the direction of the standard current, our thumb can indicate the pole of the coil.

Q.7. once a straight current-carrying conductor is placed during a magnetic filed, it experiences a force. however will this force be increased?

Ans. an electrical current produces a magnetic flux like that of a static magnet. Since a magnetic flux exerts a force on a static magnet, it implies that current-carrying wire ought to conjointly expertise a force once placed during a magnetic flux.

Michael Faraday discovered that the force on the wire is at right angles to each the direction of the magnetic flux and therefore the direction of the present. The force is exaggerated if

current within the wire is exaggerated
strength of magnetic flux is exaggerated
length of the wire within the magnetic flux is exaggerated
Q.8. Demonstrate that a straight current-carrying conductor placed during a magnetic flux experiences a force.

Ans. The force on a wire during a magnetic flux carj be incontestible by victimisation the arrangement as srfown in Fig.15.5. battery produces currepln a wire placed within the magnetic flux or a static magnet. A current-carrying wire produces its own magnetic flux that interacts with the sphere of the magnet. As a result, a force is exerted on the wire. looking on the direction of the present, the force on the wire either pushes or pulls it towards left (Fig. 15.5-a) or towards right (Fig. 15.5-b).

Fig. 1 5.5 Force on a current-carrying wire jn magnetic flux

Q.9. once a current-carrying conductor is placed during a magnetic flux, it experiences a force. State the rule by that the direction of this force are often determined. t-

Ans. determinative THE DIRECTION OF FORCE

Faraday’s description of the force on a current-carrying wire doesn’t fully specify the direction of force as a result of the force are often towards left or towards right. The direction of the force on a current-carrying wire during a magnetic flux are often found by victimisation Fleming’s manus rule.

It is declared that:

Stretch the thumb in such how that, index finger and therefore the finger of the manus ar reciprocally perpendicular to every different If the index finger points within the direction of the magnetic flux, the center finger within the direction of the present, then the thumb would indicate the direction of the force performing on the conductor.

As shown in Fig. 15. 6, the force performing on the conductor is at right angle to each the directions of current and magnetic flux in accordance with the Fleming’s manus rule.

Force

Q.1 D. justify that a current-carrying coil during a magnetic flux experiences a force or turning result.

Ans. force OR TURNING result ON A CURRENT-CARRYING COIL during a magnetic flux

Consider an oblong coil of wire with sides PQ AN SR, lying perpendicular to the sphere, placed between the 2 poles of a static magnet currently if the ends of the coil ar connected with the positive and negative terminals of battery, a current would begin flowing through the coil. the present passing through the loop enters from one finish of the loop and leaves from the opposite finish.

Armatu

Rotation

Magnet

battery

A current-carrying coil during a magnetic flux.

Now apply Fleming’s manus rule to every facet of the coil (Fig. 15.7). we are able to see that on PQ facet of the loop force acts upward, whereas on the SR facet of the loop, force acts downward. it’s as a result of the direction of the present through the 2 sides of the loop facing the 2 poles is at right angles to the sphere however opposite to every different. the 2 forces that ar equal in magnitude however opposite in direction type some The ensuing force thanks to this couple rotates the loop, and therefore the magnitude of the force performing on the loop is proportional to the magnitude of the present passing through the loop. If we have a tendency to increase the amount of loops, the turning result is greatly exaggerated

0.11. what’s an electrical motor? justify the working rule of D.C. motor. An*. an electrical MOTOR

An electrical motor converts electric energy into move K.E

Working Principle of D.C.Motor

It is pricey type the figure that he straightforward coil placed during a magnet cannot rotate rndre than 90° The forces push the PQ facet of the coil up and therefore the SR facet of the loop down till the loop reaches the vertical position. during this scenario, plane of the loop is perpendicular to the magnetic flux and therefore the web force on the coil is zero. that the loop won’t still come as a result of the forces ar still up and down and balanced.

armature

rotation

magnet

battery

How will we have a tendency to rotate the coil

continuously by reversing the direction of the present even as the coil reaches its vertical position. This reversal of current can enable the coil to rotate endlessly. To reverse direction of current, the association to the coil is created through a meeting of brushes and a hoop that’s split into 2 halves, known as a split ring switch. Bruishes, that ar typically items of atomic number 6, create contact with the switch and permit current to flow into the loop. because the loop rotates, thus will the switch. The split ring is organized so every halfof the commuator changes brushes even as the coil reaches the vertical position. ever-changing brushes, reverse the present within the loop.

As a result, the direction of the force on either side of the coil is reversed and it continuous to rotate. This method repeats at every half-turn, .causing the coil to rotate within the magnetic flux endlessly. The result’s an electrical motor, that is AN equipment that converts electrical energy into move mechanical energy.

Q.12. however the entire force performing on the coil are often increased?

Ans. during a sensible motor, the coil, known as the coil, is created of the many loops mounted on a shaft or shaft. The magnetic flux is made either by permanent magnets or by AN magnet, known as a coil. The force on the coil, and, as a result, the speed of the motor, is controlled by variable the present through the motor.

The total force performing on the coil are often exaggerated by –

increasing the amount of activates the coil
increasing the present within the coil.
increasing the strength of the magnetic flux.
increasing the realm of the coil.
Q.W. What does one mean by magnetic attraction induction and strength of a magnetic field?

Ans. magnetic attraction INDUCTION

The process of generating AN induced current during a circuit by ever-changing the amount of magnetic lines of force passing through it’s caHed magnetic attraction induction.

STRENGTH OF A FIELD

The number of magnetic lines of force passing through any surface in called strength of magnetic flux,

Q.14. justify that the amount of magnetic lines of force depends upon the position of the surface.

Ans. the amount of lines of force is most once the surface is command perpendicular to the magnetic lines of force (Fig. 15.9). it’ll be minimum once the surface is command parallel to the magnetic lines of force.

Q.I5. justify that the amount of magnetic lines of force rely on the space of the coil.

Ans. If we have a tendency to place a coil within the magnetic flux of a magnet, a number of the magnetic lines of force can labor under it. If the coil is way far from the magnet, solely a number of lines of force can labor under the coil (Fig.15 11-a) but, if the coil is nearer to the magnet, an oversized numberpf lines of force can labor under it (Fig. 15 11-b).

(a)

Variation of magnetic flux lines of force through a coil placed at totally different distances from tried magnet.

This means, we are able to modification the amount of magnetic lines of force through a coil by moving it within the magnetic flux. this alteration within the variety of magnetic flux lines can induce AN e.m.f. within the coil this can be the fundamental principle of production of electricity and dealing of a electrical device

Q.16. Describe an easy experiment to demonstrate that a ever-changing magnetic flux will induce AN e.m.f. during a circuit.

Ans. Fig.15.12 shows one among Faraday’s experiments within which current is induced by moving a magnet into the coil or out of the coil once the magnet is stationary, no current is induced once the magnet is enraptured towards the coil, the needle of the meter deflects towards right, indicating that a current is being induced within the coil. once the magnet is force far from the coil, the meter deflects towards left, indicating that the induced current within the coil is within the wrong way.