Students can Download Science Chapter 13 Magnetic Effects of Electric Current Questions and Answers, Notes Pdf, KSEEB Solutions for Class 10 Science helps you to revise the complete Karnataka State Board Syllabus and to clear all their doubts, score well in final exams.
Karnataka State Syllabus Class 10 Science Chapter 13 Magnetic Effects of Electric Current
KSEEB Class 10 Science Magnetic Effects of Electric Current Intext Questions and Answers
Question 1.
Why does a compass needle get deflected when brought near a bar magnet?
Answer:
A compass needle gets deflected when brought near a bar magnet.
∴ force is exerted by the bar magnet on the compass needle, which is itself a tiny pivoted magnet.
Question 2.
Draw magnetic field lines around a bar magnet.
Answer:
Question 3.
List the properties of magnetic lines of force.
Answer:
- Magnetic field lines are closed curves.
- No two field-lines are found in cross each other.
- The relative strength of the magnetic field is shown by the degree of closeness of the fieldlines.
Question 4.
Why don’t two magnetic lines of force intersect each other?
Answer:
No two field-lines are found to cross each other. If they did, it would mean that at the point of intersection, the compass needle would point towards two directions, which is not possible.
Question 5.
Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.
Answer:
In this experiment, direction of magnetic field is inside means inside of table. Similarly in the outside means outside of table there is magnetic field.
Question 6.
The magnetic field in a given region is uniform. Draw a diagram to represent it
Answer:
A uniform magnetic field in a region is represented by drawing parallel and equidistant straight lines, all pointing in the same direction.
Question 7.
Choose the correct option.
The magnetic field inside a long straight solenoid-carrying current
(a) is zero.
(b) decreases as we move towards its end.
(c) increases as we move towards its end.
(d) is the same at all points.
Answer:
The field lines inside the solenoid are in the form of parallel straight lines. This 3 indicates that the magnetic field is the same at all points inside the solenoid. Thus answer (d) is correct.
Question 8.
Which of the following property of a proton can change while it moves freely in a magnetic field?
[There may be more than one correct answer.]
(a) mass
(b) speed
(c) velocity
(d) momentum
Answer:
Whenever a charged particle, in this case, a proton moves in a magnetic field, its velocity and as a result of this its momentum change. Thus, (iii) and (Iv) are the properties which change when a proton moves freely in a magnetic field.
Question 9.
In Activity 13.7, how do we think the displacement of rod AB will be affected if
(1) Current in rod AB is increased;
(2) a stronger horse-shoe magnet is used
(3) length of the AB rod is increased.
Answer:
- When the current in the rod AB is increased, the force exerted on the conductor increases, so the displacement of the rod increase.
- When a stronger horseshoe magnet is used, the magnitude of the magnetic field increases. This increases the force exerted on the rod and the displacement of the rod.
- The displacement of the rod will increase because of F α L
Question 10.
A positively-charged particle (alpha- particle) projected towards the west is deflected towards north by a magnetic field. The direction of the magnetic field is
(a) towards south
(b) towards east
(c) downward
(d) upward
Answer:
Since the positively charged particle alpha particle projected towards west, so the direction of current is towards west. Now the deflection is towards north, so the force is towards north. Now hold the fore finger, centre finger and thumb of our left – hand at right angles to one another. Let us adjust the hand in such a way that our centre finger points towards west and thumb points towards north. If we look at our forefinger, it will be pointing, upward. Thus, the magnetic field is in the upward direction. So, the correct answer is (iv)
Question 11.
State Fleming’s left-hand rule.
Answer:
Stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular. If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.
Question 12.
What is the principle of a electric motor?
Answer:
A current-carrying conductor when placed in the magnetic field experiences a force, the direction of this force is given by fleming’s left-hand rule. This is the basis of an electric motor.
Question 13.
What is the role of the split ring in an electric current?
Answer:
In electric motors, the splittings acts as a commulator. The reversal of current also reverses the direction of force acting on the two arms AB and CD. The reversing of the current is repeated at each half rotation, giving rise to a continuous rotation of the coil and to the axle.
Question 14.
Explain different ways to induce current in a coil.
Answer:
The different ways to induce current are as follows:
- Moving a magnet towards a coil sets up a current in the coil circuit.
- If a coil is moved rapidly between the two poles of a horse-shoe magnet, then an electric current is induced in the coil.
Question 15.
State the principle of an electric generator.
Answer:
An electric generator works on the principle of electromagnetic induction. When a closed coil is rotated in a uniform magnetic field with its axis perpendicular to the direction of the field, the magnetic field lines passing through the coil change and an induced potential difference and hence a current is set – up in it.
Question 16.
Name some sources of direct current.
Answer:
Some of the sources of direct current are dry cell battery, car battery and dc generator.
Question 17.
Which sources produce alternating current?
Answer:
Some of the sources that produce alternating current are bicycle dynamos, car alternators and power house generate.
Question 18.
Choose the correct option.
A rectangular coil of copper wires is rotated in a magnetic field. The direction of the induced current changes once in each
(a) two revolutions
(b) one revolution
(c) half revolution
(d) one-fourth revolution
Answer:
(c) half revolution
Question 19.
Name two safety measures commonly used in electric circuits and appliances.
Answer:
- Electric fuse
- Earthing of metal bodies of electrical appliances.
Question 20.
An electric oven of 2kW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.
Answer:
Power,P = 2kW = 2x 1000 W = 2000W
Voltage, V = 220 V
Current drawn, I = ?
Power, P = V x I°
\(I=\frac{P}{V}=\frac{2000}{220}=9 \mathrm{A}(\text { approx })\)
The current drawn by this electric oven is 9 A whereas the fuse in the circuit is ( only 5 A capacity. When a high current of 9 A flows through the 5 A fuse, the fuse wire will get heated too much, melt and break, the circuit. Therefore, when a 2 kW power rating electric oven is operated in a circuit having a 5 A fuse will blow off cutting off the power supply in this circuit.
Question 21.
What precaution Should be taken to avoid the overloading of domestic electric circuits?
Answer:
- Too many electrical appliances should not be operated on a single socket.
- Too many high power rating electrical appliances should not be switched on at the same time.
KSEEB Class 10 science Magnetic Effects of Electric Current Textbook Exercise Questions and Answers
Question 1.
Which of the following correctly describes the magnetic field near a long straight wire?
(a) The field consists of straight lines perpendicular to the wire.
(b) The field consists of straight lines parallel to the wire.
(c) The field consists of radial lines originating from the wire.
(d) The field consists of concentric circles centred on the wire.
Answer:
(d) The field consists of concentric circles centred on the wire.
Question 2.
The phenomenon of electromagnetic induction is
(a) the process of charging a body.
(b) the process of generating a magnetic field due to current passing through a coil.
(c) Producing induced current in a coil due to relative motion between a magnet and the coil.
(d) the process of rotating a coil of an electric motor.
Answer:
(c) Producing induced current in a coil due to relative motion between a magnet and the coil.
Question 3.
The device used for producing electric current is called a
(a) generator
(b) galvanometer
(c) ammeter.
(d) motor.
Answer:
(a) generator
Question 4.
The essential difference between an AC generator and a DC generator is that
(a) AC generator has an electromagnet while a DC generator has a permanent magnet.
(b) DC generator will generate a higher voltage.
(c) AC generator will generate a higher voltage.
(d) AC generator has slip rings while the DC generator has a commutator.
Answer:
(d) AC generator has slip rings while the DC generator has a commutator
Question 5.
At the time of short circuit, the current in the circuit
(a) reduces substantially
(b) does not change
(c) increases heavily
(d) vary continuously.
Answer:
(c) increases heavily
Question 6.
State whether the following statements are true or false.
(a) An electric motor converts mechanical energy into electrical energy.
(b) An electric generator works on the principle of electromagnetic induction.
(c) The field at the centre of a long circular coil carrying current will be parallel straight lines.
(d) A wire with a green insulation is usually the live wire of electric supply.
Answer:
(a) False. It converts electrical energy into mechanical energy.
(b) True
(c) True. The field is almost uniform at the centre of the coil,
(d) False. The wire with green insulation is usually the live wire.
Question 7.
List two methods of producing magnetic fields.
Answer:
Permanent magnets, electromagnets and earth’s magnetic field.
Question 8.
How does a solenoid behave like a magnet? Can you determine the north and south poles of a current-carrying solenoid with the help of a bar magnet? Explain.
Answer:
The patterns of the magnetic fields of both the solenoid and a bar magnet are . exactly similar. Like a bar magnet, one end of the solenoid has N – polarity and the other end S – polarity. We bring the N – pole of the bar magnet near one end of the solenoid : If there is an attraction, then that end of the solenoid has south polarity and other has north polarity. If there is a repulsion, then that end of the solenoid has north polarity and the other end has south polarity.
Question 9.
When is the force experienced by a current-carrying conductor placed in a magnetic field largest?
Answer:
When the conductor carries current in a direction perpendicular to the direction of the magnetic field, the force experienced by the conductor is largest.
Question 10.
Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?
Answer:
As per Flemings left hand rule the direction of magnetic field is down.
Question 11.
Draw a labelled diagram of an electric motor. Explain its principle and.working. What is the function of a split ring in an electric motor?
Answer:
“Motor works on the principle that a current carrying conductor kept in a magnetic field experiences mechanical force” The function of split ring, it reverses the direction of flow of current and also reverses the forces acting on the arms of AB and CD of the motor this makes coil to rotate.
- N, S Magnetic poles
- ABCD coil or armature.
- B1, B2 brushes
- S1, S2 Split rings
- I – D.C Source.
Question 12.
Name some devices in which electric motors are used.
Answer:
Electric motor is used in appliances like electric fans, washing machines, mixers, grinder, blenders, computer, MP3 players etc.
Question 13.
A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is
(1) pushed into the coil
(2) withdrawn from inside the coil
(3) held stationary inside the coil?
Answer:
- An electric current is induced in the coil and the galvanometer shows a deflection.
- An electric current is induced in the coil but in opposite direction. The galvanometer shows a deflection in reverse direction.
- No current is induced in the coil. The galvanometer shows no deflection.
Question 14.
Two circular coils A and B are placed closed to each other. If the current in the coil A is changed, will some current be induced in coil B? Give reason.
Answer:
Yes, when the current in coil A is changed, some current is induced in the coil B. Due to the change in current in coil A, the magnetic field lines linked with coil A and with coil B get changed. This sets up induced current in coil B.
Question 15.
State the rule to determine the direction of a
(i) magnetic field produced around a straight conductor carrying current,
(ii) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and
(iii) current induced in a coil due to its rotation in a magnetic field.
Answer:
- Maxwell’s Right-hand rule.
- Fleming’s Left-hand rule.
- Fleming’s Right-hand rule.
Question 16.
Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?
Answer:
The Dynamo works on the principle of electromagnetic induction which is when there is change of magnetic field linking the coil it induces electromagnetic field. The brushes maintain sliding contact through these e.m.f flows.
- SN magnetic poles
- ABCD coil or Armature.
- B1, B2 brushes
- S1,S2 Split rings
- L Lamp
Question 17.
When does an electric short circuit occur?
Answer:
As a result of live wire touching the neutral wire, the resistance offered to the flow of current becomes almost zero and this is called short-circuiting. In this situation, a large current flows through the circuit causes a spark or damage to the appliance.
Question 18.
What is the function of an earth wire? Why is it necessary to earth metallic appliances?
Answer:
The earth wire connects the metallic body of the high powered appliance to the earth. It is a safety measure which ensures any leakage of current of the metallic body of the appliance keeps its potential equal to that of the earth (zero volt) and the user may not get a severe electric shock.
Multiple Choice, Questions:
Question 1.
The magnetic lines of force
(a) always intersect each other
(b) never intersect each other
(c) sometimes intersect and sometimes do not intersect
(d) are always parallel to each other.
Answer:
(b) never intersect each other
Question 2.
A charged body at rest produces.
(a) electric field only
(b) magnetic field only
(c) neither electric field nor magnetic field
(d) both electric and magnetic field.
Answer:
(a) electric field only
Question 3.
The magnetic lines of force of a straight conductor carrying current are
(a) parallel to conductor
(b) concentric circles
(c) perpendicular to conductor
(d) none of these.
Answer:
(b) concentric circles
Question 4.
The magnetic effect of current was discovered by
(a) Faraday
(b) Henry
(c) Oersted
(d) Maxwell
Answer:
(b) Henry
Question 5.
An electric generator actually acts as
(a) a source of electric charge
(b) a source of heat energy
(c) an electromagnet
(d) a converter of energy.
Answer:
(d) a converter of energy.
Question 6.
The device based on the principle of electromagnetic induction is
(a) electric generator
(b) electric motor
(c) voltmeter
(d) ammeter
Answer:
(a) electric generator
Question 7.
An electric motor
(a) generates electric energy
(b) generates mechanical energy.
(c) converts mechanical energy into electrical energy
(d) converts electrical energy into mechanical energy
Answer:
(d) converts electrical energy into mechanical energy
Question 8.
Current carrying conductor placed in a magnetic field experiences a force. The device based on this principal is.
(a) electrical generator
(b) electric motor
(c) electric bell
(d) none of these.
Answer:
(b) electric motor
Question 9.
The frequency of A.C mains used in India is
(a) 30 cps
(b) 50 cps
(c) 60 cps
(d) 120 cps
Answer:
(b) 50 cps
Question 10.
Magnetic fields do not interact with
(a) electric charges at rest.
(b) electric charges in motion.
(c) permanent magnets at rest
(d) permanent magnets in motion.
Answer:
(a) electric charges at rest.
Question 11.
The force on a charged particle is moving in a magnetic field is maximum when the angle between the direction of motion and field is …………..
(a) zero
(b) 90°
(c) 180°
(d) 45°
Answer:
(b) 90°
KSEEB Class 10 Science Magnetic Effects of Electric Current Additional Questions and Answers
Question 1.
On what effect of an electric current does an electromagnet work?
Answer:
An electromagnet works on the magnetic effect of current.
Question 2.
What is Solenoid?
Answer:
Solenoid is a coil of many turns of wire, wrapped in the shape of a cylinder.
Question 3.
Which effect of electric current is utilised in the working of an electric fuse?
Answer:
An electric fuse works on the heating effect of current.
Question 4.
How is the strength of the magnetic field at a point near a wire related to the strength of the electric current flowing in the wire?
Answer:
The magnitude of magnetic field is directly proportional to the strength of the electric current flowing in the wire.
Question 5.
How is the fuse connected in an electric circuit?
Answer:
Fuse is connected in series in the circuit.
Question 6.
What kind of, magnetic field is produced by a current-carrying Solenoid?
Answer:
The magnetic field produced by a current-carrying Solenoid is similar to the magnetic field produced of a bar magnet.
Question 7.
State Faraday’s law of electromagnetic induction.
Answer:
Whenever the magnetic field lines liked with a coil change due to relative motion of a magnet and the coil, an induced current is produced in the coil. The magnitude of the induced current is directly proportional to the rate of change of magnetic field lines.
Question 8.
Name the device which converts mechanical energy into electrical energy.
Answer:
Electric generator.
Question 9.
How does the strength of the magnetic field at the centre of a circular coil of a wire depend on:
(a) radius of the coil
(b) number of turns in the coil
Answer:
(a) More the radius weaker the field.
(b) Field strength is directly proportional to the number of turns in the coil.
Question 10.
How can the magnitude of the induced current be increased?
Answer:
The magnitude of the induced current can be increased by:
- Taking the conductor in the form of a coil of many turns of insulted wire.
- Increasing the strength of the magnetic field used.
- Increasing the rate of change of magnetic flux associated with the coil.
Question 11.
Explain what is short circuiting and overloading in an electric supply.
Answer:
Short circuiting: Whenever live and neutral wires come in contact with each other, the incident is called short circuiting. In this case, resistance of a circuit decreases to a very small value; The decreasing of resistance increases the current. Due to this increased current, the wires get heated. This extreme heat may cause fire in the building.
Over loading: Every supply has a capacity to bear a maximum load, i.e., the power that can be supplied has a limit. Sometimes, the number of appliances which are switched on at the same time have power, more than the capacity of the line. This is called overloading. In this situation, wires of the supply get heated due to extremely large current flowing through them and the circuit may catch fire. To avoid this fire, we use an electric fuse in the circuit.
Question 12.
With the help of a diagram, describe an experiment to show that a change in current flowing through a coil includes an electric current in a neighbouring coil.
Answer:
Take two different coils of insulated copper wire having large number of turns (50 or even more). Insert the coils over a non-conducting cylindrical thick paper roll as shown in figure. Connect a battery of 6V, a plug key K in series of coil – 1. With coil – 2, connect a sensitive galvanometer. Now put coil – 2 also gives a momentary deflection and then pointer quickly returns to its mean position.
On removing plug from key K in coil-1 the needle momentarily moves, but to the opposite side. It means that now the current flows in the opposite direction in coil-2. So we conclude that current is produced in coil-2 whenever the current flowing in the neighbouring coil is changing.