CBSE Class 10 Science Magnetic Effects of Electric Current Worksheet Set H

ONE MARK QUESTIONS

Question: What does the direction of thumb indicate in the right-hand thumb rule?
Answer: Thumb points the direction of current in the conductor holding a straight conductor in right hand.

Question: How is the magnetic field produced in a solenoid used?
Answer: Magnetic field produced in a solenoid can be used in making a soft iron piece electromagnet.

Question: Mention the angle between a current carrying conductor and magnetic field for which the force experienced by this current carrying conductor placed in magnetic field is largest?
Answer: If the angle between a current carrying conductor and magnetic field is 90° then the force experienced by the conductor is maximum.

Question: Write any one method to induce current in a coil.
Answer: By moving a magnet towards the coil or vice versa, current can be induced in the coil.

Question: When is the force experienced by a current carrying conductor placed in a magnetic field the maximum?
Answer: A current carrying conductor experience maximum force in a magnetic field when the direction of current is perpendicular to the magnetic field.

Question: State the rule which you use to find the direction of induced current or state Fleming’s right hand rule.
Answer: Fleming’s right hand rule gives the direction of current produced in a conductor. According to Fleming’s right hand rule, if we stretch right hand thumb, forefinger and middle finger perpendicular to each other in such a way that thumb points the direction of force on a conductor and forefinger points the direction of magnetic field then middle finger will point the direction of current produced in the conductor.

Question: Suggest one way of discriminating a wire carrying current from a wire carrying no current.
Answer: When a magnetic compass is brought near a current carrying conductor it will be deflected. If magnetic compass remains undeflected near a conductor then there is no current in it.

Question: How can you show that the magnetic field produced by a given electric current in the wire decreases as the distance from the wire decreases?
Answer: If we bring a magnetic compass from a distance to near a current carrying conductor its deflection goes on increasing and when magnetic compass is brought away from the current carrying wire its deflection goes on decreasing which shows that magnetic field near current carrying wire is maximum and decreasing on increasing the separation.

TWO MARKS QUESTIONS

Question: State one main difference between ac and dc. Why ac is preferred over dc for long range transmission of electric power? Name one source each of dc and ac.
Answer: The magnitude and direction of ac remains same whereas a.c. changes its magnitude and direction periodically. Low AC voltage can be increase to high voltage to prevent loss in electric energy during its long distance transmission. AC generator and DC generator/or cell.

Question: Why does a current carrying Conductor experiences a force when it is placed in a magnetic field? State Fleming’s left hand rule.
Answer: When a current carrying conductor is placed in a magnetic field it experiences a force due to interaction between the two magnetic fields due to current carrying , conductor and given magnetic field of a magnet. If we hold our thumb, forefinger, and middle finger perpendicular to each other in such a way that forefinger points the direction of magnetic field, middle finger points the direction of charge q (direction of current in conductor), then thumb will point the direction force acting upon the conductor.

Question: Name any three factors on which the magnitude of the magnetic field due to solenoid depends.
Answer: Factors on which the magnitude of the magnetic field due to solenoids
a. number of turns in the solenoid
b. area of cross section of the coil
c. strength of current in solenoid 

Question: A student performs an experiment to study the magnetic effect of current around a current carrying straight conductor with the help of a magnetic compass. He reports that:
a. the degree of deflection of the magnetic compass increases when the compass is moved away from the conductor.
b. the degree of deflection of the magnetic compass increases when the current through the conductor is increased.
Which of the above observations of the student appears to be wrong and why?
Answer: The first statement is wrong because the strength of magnetic field decreases when we move away from a current carrying conductor. So deflection in the compass, instead of increasing must decrease.

Question: What is meant by the term magnetic field lines? List any two properties of magnetic field lines.
Answer: The imaginary path traced by N-pole of a magnet in a magnetic field is called magnetic field lines. Properties:
a. Two magnetic field lines never intersect each other.
b. Magnetic field lines are crowded near the poles and near the mid part of magnets the density of magnetic lines of force decreases.

Question: (a) What is the direction of magnetic field lines inside a bar magnet and outside of it?
(b) What does the degree of closeness of the field lines represent?
Answer: The direction of magnet lines of force inside a bar magnet is from S-pole to N-pole. 

Question: What does the direction of thumb indicate in the right hand thumb rule? In what way this rule is different from Fleming’s left hand rule?
Answer: Thumb indicate the direction of current in a straight conductor held in right hand. Fleming’s left hand rule gives the direction of force on a current carrying conductor placed in magnetic field. 
Fleming’s left hand rule : If we stretch right hand thumb, forefinger and middle finger perpendicular to each other in such a way that forefinger points the direction of magnetic field, middle finger points the direction of current, then thumb will point the direction of force on the conductor. 

Question: 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: Magnetic field strength at the centre of a circular coil
of a wire carrying current
a.∝1/r, i.e. magnetic field decreases with increase in radius.
b. ∝ n, i.e. magnetic field increases with increase in number of turns.

Question: Name two safety measures commonly used in electric circuits and appliances, what precautions should be taken to avoid the over loading of domestic electric circuits?
Answer: Proper earthing and using a fuse load in the electric circuit must be as per rating of the fuse and do not connect to many plugs in a single socket.

Question: A magnetic compass shows a deflection when placed near a current carrying wire. How will the deflection of the compass get affected if the current in the wire is increased? Support your answer with a reason.
Answer: If current is increased magnetic field around this conductor increases, the deflection in the galvanometer also increases.

Question: A coil made of insulated copper wire is connected to a galvanometer. What will happen to the deflection of the galvanometer if this coil is moved towards a stationary bar magnet and then moved away from it? Give reason for your answer and name the phenomenon involved.
Answer: In both the case there is a change in magnetic field associated with the coil, an induced current is produced in the coil, but in opposite direction. This phenomenon is called electromagnetic induction (EMI).

Question: Why does a current carrying conductor kept in a magnetic field experience force? On what factors does the direction of this force depend? Name and state the rule used for determination of direction of this force.
Answer: Around a current carrying conductor a magnetic field is produced. When it is placed in a magnetic field then both fields interact each other, and current carrying conductor experience a force.
Fleming’s left hand rule: If we stretch right hand thumb, forefinger and middle finger perpendicular to each other in such a way that forefinger points the direction of magnetic field, middle finger points the direction of current, then thumb will point the direction of force on the conductor.

Question: A magnetic compass shows a deflection when placed near a current carrying wire. How will the deflection of the compass get affected, if the current in the wire is increased? Support your answer with a reason.
Answer: If the strength of current is increased then deflection of compass also increase because magnetic field is directly proportional to the current in the conductor. More magnetic field more deflection in the compass.

Question: (a) Mention the colour code used for live, neutral and earth wire.
(b) You want to connect a 2 kW electric oven in the electric circuit. In which power line would you connect it and why? What may happen if you
connect it wrongly in the other power line?
Answer: (a) Live wire – Red
Neutral wire – Black
Earth wire – Green
(b) 2 kW electric iron draws large current. If it is connected to a socket of 5Athen fuse will be blown. So it is connected in power socket of 15 A.

Question: Write one difference between direct current and alternating current. Which one of the two is mostly produced at power stations in our country? Name one device which provides alternating current. State one important advantage of using alternating current.
Answer: Direct current has constant magnitude and unidirectional current. Alternating current changes its magnitude and direction alternatively.
a. Alternating current is produced in power stations in India.
b. AG generators are used to produce AC.
c. AC voltage can be increased or decrease with the help of a transformers.

Question: Define a solenoid. How is it different from a coil?
Answer: A coil of many circular turns of insulated wire wrapped closely in the form of a cylinder is called a solenoid.
In a current carrying solenoid magnetic field is same at all points inside it, i.e. field is uniform inside the solenoid. The magnetic field inside a coil vary.

Question: A compass needle is placed near a current carrying wire. State your observation for the following cases and give reason for the same in each case:
a. Magnitude of electric current in the wire is increased.
b. The compass needle is displaced away from the wire.
Answer: a. Compass needle is deflected more because more the current, more the magnetic field near the wire.
b. Magnetic field strength is inversely proportional to the distance from current carrying wire. So deflection will decrease in the compass needle
when brought away from wire.

Question: What is meant by overloading of an electrical circuit? Explain two possible causes due to which overloading may occur in household circuit. Explain one precaution that should be taken to avoid the overloading of domestic electric circuit.
Answer: Connecting large number of electric appliances in one socket whose load is more than the aximum permitted limit. The two possible cause are a. all of a sudden supply of high voltage and b. too many devices connected in a ingle socket. 
Precautions:
a. use of voltage regulator, b. load of a socket must be greater than its permitted rating.

FIVE MARKS QUESTIONS

Question: (a) State Fleming’s left hand rule.
(b) Write the principle of working of an electric motor.
(c) Explain the function of the following parts of anelectric motor.
(i) Armature (ii) Brushes (iii) Split ring
Answer: (a) Fleming’s left hand rule state that if the thumb, forefinger and middle finger are stretched perpendicular to each other in such a way that forefinger indicates the direction of magnetic field, middle finger indicate the direction of current in the conductor then thumb will indicate the direction of force on the conductor.
(b) The principle of electric motor is that when a current carrying coil is placed in a magnetic field it experiences a torque and if the coil is allowed it rotates in the magnetic field. 
(c) Function of the parts of an electric motor : 
(1) Armature: Armature is a large number of turns of the coil on soft iron core which rotates in magnetic field.
(2) Brushes: They allow current to pass from external source to armature.
(3) Split rings: Split rings are of copper, splits into two halves and make a connection between armature and brushes.

Question: Explain the meanings of the words “electromagnetic” and “induction” in the term electromagnetic induction. List three factors on which the value of induced current produced in a circuit depends. Name and state the rule used to determine the direction of induced current. State one practical application of this phenomenon in everyday life.
Answer: The word electromagnetic means that an electric potential dipole is being produced in a coil due to change in magnetic field. The word induction means that the current has been induced. The value of induced current produced in a circuit depends on the following factors:
a. number of turns in given coil
b. area of each turn in coil
c. rate of change of magnetic field.
The rule is Fleming’s right hand rule. Stretch the thumb, forefinger and middle finger of righthand perpendicular to each other that forefinger indicates the direction of magnetic field, thumb gives the direction of motion (or force) of the conductor, then middle finger will point the direction of induced current.
Application: AC generator or DC generator.

Question: (a) What is meant by a ‘magnetic field’?
(b) How is the direction of magnetic field at a point determined?
(c) Describe an activity to demonstrate the direction of the magnetic field generated around a current carrying conductor.
(d) What is the direction of magnetic field at the centre of a current carrying circular loop?
Answer: a. Magnetic field is the space around a magnet or a current carrying conductor in which its magnetic force can be experienced.
b. A magnetic compass is used to demonstrate the direction of the magnetic field generated around a current carrying conductor.
c. Fix a cardboard and insert a wire to pass through its centre normal to the plane of the card board. Sprinkle iron filings on card board uniformly. Pass the current in the wire. Tap the cardboard gently. You will find that iron filings align themselves in the concentric circles around the wire. These circles represents magnetic field lines around the conductor.

Question:(a) An electric current is passed in a horizontal copper wire from east to west. Explain your observations when a compass needle is placed (i) below this wire,
(ii) above the wire. Draw inference from your observations.
(b) List the factors on which the strength of the magnetic field due to a straight conductor carrying current depend. How should these be changed to decrease magnetic field at a point?
Answer: (a) The direction of deflection of a magnetic compass needle depends upon the direction of the magnetic field at that point. The direction of the magnetic field due to a current carrying wire is given by the right hand screw rule. The direction of magnetic field below and above the wire is opposite so deflection in compass needle changes as well i.e, the deflection is reverse direction.
(b) The factors affecting strength of the magnetic field due to a straight wire carrying current:
1. magnitude of current in the wire ∝ I
2- distance of the point from the wire ∝1/I
By decreasing current or increasing the distance of the point from the wire, strength of magnetic field also decreases.

Question: (a) Explain any three properties of magnetic field lines.
(b) Give two uses of magnetic compass.
Answer: (a) Properties of magnetic field lines:
1. Magnetic field lines emerge from N pole and merge at S pole outside a bar magnet and travel from S pole to N pole inside the magnet.
2. These are continuous and closed curves.
3. Two field lines never intersect each other.
(b) Uses of magnetic compass :
1. In navigation it is used to find direction.
2. It is used to detect the magnetic field.
3. It can be used to test whether a substance is magnetic or not.

Question: (a) Explain what is the difference between direct current and alternating current? Write one Download more materials in free at : 
important advantage of using alternating current.
(b) An air conditioner of 2 kW is used in an electric circuit having a fuse of 10 A rating. If the potential difference of the supply is 220 V, will the fuse be able to withstand, when the air conditioner is switched on? Justify your answer.
Answer: (a) Direct current is a unidirectional current with constant magnitude. Alternating current is a current which change its magnitude and direction
after a fixed period. AC voltage can be increased or decreased. Where is dc voltage cannot be increased or decreased. AC can be transmitted to
long distances with lesser power loss.
(b) Given P = 2 kW and V = 200 volt, 
Power, P= VI ⇒ I = p/v
I =2000/220=9.09A
The rating of the fuse wire is 10 A which is greater than current drawn by air conditioner so when air conditioner is switched on, fuse will not blow off.

Question: (a) What is an electromagnet? What does it consist of?
(b) Name one material in each case which is used to make a : (i) permanent magnet (ii) temporary magnet.
(c) Describe an activity to show how you can make an electromagnet in your school laboratory.
Answer: a. A soft metal core made into a magnet by the passage of electric current through a coil surrounding it. It consists a soft iron core or its alloy and a solenoid conductor coil around the core.
b. (i) To make a permanent magnet alloy Alnico is used. (ii) Soft iron is used to make temporary magnet.
c. Take a long nail and put it into a solenoid of insulated copper wire. Pass the strong current in the solenoid the nail inside the solenoid becomes magnetised. This is called electromagnet.

Question: (a) State the function of ‘a fuse’ in an electric circuit. How is it connected in the domestic circuit?
(b) An electric fuse of rating 3A is connected in a circuit in which an electric iron of power 1.5 kilo watt is connected which operates at 220 V. What would happen? Explain.
Answer: (a) Fuse is a safety device to prevent the damage of electrical devices from short circuit or overloading.
A fuse is connected in series with the circuit.
(b) Given Power P = 1.5 kW = 1500 Watt and V = 220 Volts.
Power P VI ⇒I=p/v=1500/220=6.8 A
The rating of fuse is 3A which is lesser the current drawn by electric iron 6.8 A. So fuse wire will be blown.

Question: (a) Name two electrical appliances of daily use in which electric motor is used.
(b) Name and state the principle on which an electric motor works.
Answer: (a) Drill machine, fan, grinder
(b) An electric motor works on the Fleming’s left hand rule. When a current carrying coil is placed in a magnetic field it experience a torque due to which it rotates.
Fleming’s left hand rule-stretch left hand, thumb, forefinger and middle finger perpendicular to each other in such a way that forefinger indicates the direction of magnetic field, middle finger indicates the direction of current in the conductor then thumb will point the direction of force on the conductor,