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

Magnetic Effects of Electric Current

Multiple Choice Questions

Question. 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: (d)

Question. Which of the following property of a proton can change while it moves freely in a magnetic field?
(a) Mass
(b) Speed
(c) Velocity
(d) Charge
Answer: (c)

Question. A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is :
(a) towards south
(b) towards east
(c) downward
(d) upward
Answer: (d)

Question. 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)

Question. 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)

Question. The phenomenon of electromagnetic induction is :
(a) the process of charging a body.
(b) the process of generating magnetic field due to a 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)

Question. The device used for producing electric current is called a :
(a) generator
(b) galvanometer
(c) ammeter
(d) motor
Answer: (a)

Question. The essential difference between an A.C. generator and a D.C. generator is that :
(a) A.C. generator has an electromagnet while a D.C. generator has permanent magnet.
(b) D.C. generator will generate a higher voltage.
(c) A.C. generator will generate a higher voltage.
(d) A.C. generator has slip rings while the D.C. generator has a commutator.
Answer: (d)

Question. 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)

Question. The direction of force acting on a current carrying conductor placed in a magnetic field can be obtained by :
(a) Fleming’s left hand rule.
(b) Fleming’s right hand rule.
(c) Clock face rule.
(d) Ampere’s swimming rule.
Answer: (a)

Question. Match the following
Column I
(a) Direction of magnetic field for current carrying wire
(b) Direction of force acting on current carrying conductor.
(c) Direction of induced current in a conductor.
(d) Polarity of two faces of current carrying loop.
Column II
(i) Fleming’s left hand Rule.
(ii) Clock face rule
(iii) Right-Hand Thumb rule
(iv) Fleming’s Right-Hand rule
Answer: (a) (iii), (b) (i), (c) (iv), (d) (ii).

Question. Fill in the blanks
(a) Fleming’s Rule for the motor effect uses the ............... hand.
(b) A fuse should always be placed in the ................ wire of a main circuit.
(c) An electric motor is a device which transform ............. energy to ............ energy.
Answer: (a) Left, (b) Live, (c) Electrical, mechanical.

Very Short Answers Type Questions

Question. What is the function of a galvanometer in a circuit ?
Answer: Galvanometer is a device that detects the presence of current in a circuit. It is also used for measuring the amount of current in the circuit.

Question. Define magnetism.
Answer: The property by virtue of which a magnet attracts certain metals such as iron, cobalt, nickel etc., is termed as magnetism.

Question. What do you mean by ‘magnetic field’ of a magnet ?
Answer: The space or region around a magnet in which the force of attraction or repulsion due to the magnet can be detected is called the magnetic field.

Question. What is a solenoid ?
Answer: A solenoid is a long coil containing a large number of close turns of insulated copper wire.

Question. Define an electromagnet.
Answer: An electromagnet is a magnet consisting of a long coil of insulated copper wire wrapped around a soft iron core that is magnetised only when electric current is passed through the coil.

Question. What is a galvanometer ?
Answer: A galvanometer is an instrument which can detect the presence of electric current in a circuit.

Question. Define electromagnetic induction.
Answer: The production of electricity from magnetism is called electromagnetic induction.

Question. What is a permanent magnet ? Give one use of it.
Answer: A permanent magnet is a magnet made from steel such that once magnetised, it does not lose it magnetism easily. Use: In loudspeakers.

Question. Define a compass.
Answer: A compass is a device used to show magnetic field direction at a point. It consists of a tiny pivoted magnet usually in the form of a pointer which can turn freely in the horizontal plane.

Question. What is the difference between an A.C. generator and a D.C. generator ?
Answer: A.C. generator has slip rings while D.C. generator has a commutator.

Short Answers Type Questions

Question. Give reasons for the following :
(i) There is either a convergence or a divergence of magnetic field lines near the ends of a current carrying straight solenoid.
(ii) The current carrying solenoid when suspended freely rests along a particular direction.
(iii) The burnt out fuse should be replaced by another fuse of identical rating.
Answer: (i) When a current pass through solenoid, it creates a nearly uniform magnetic field inside or along the axis of the solenoid. Outside the coil or solenoid, i.e., at the ends and beyond the magnetic field is small and appears to diverge. This divergence is because the distance from the current carrying solenoid increases. The distance from the current carrying conductor and the magnetic field are inversely proportional i.e., as distance increases, magnetic field strength decreases.
(ii) The current carrying solenoid when suspended freely rests along a particular direction because it behaves like a bar magnet.
(iii) Fuse is the most important safety device, used for protecting the circuits due to short-circuiting or overloading of the circuits. A fuse wire works because of its lower melting point which is possible. If a fuse with larger rating is used with an appliance, the fuse wire shall not melt and hence would fail to serve the required purpose.

Question. What is an electric motor ? Name five main parts of a D.C. motor.
Answer: An electric motor is a device which converts the electrical energy into mechanical energy.
The five main parts of a D.C. motor are :
(a) Strong field magnet, (b) Armature coil,
(c) Split ring or commutator, (d) Carbon brushes, and
(e) Battery.

Question. State the rule to determine the direction of a :
(a) Magnetic field produced around a straight conductor-carrying current.
(b) Force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it.
(c) Current induced in a coil due to its rotation in a magnetic field.
Answer: (a) Right hand thumb rule or Maxwell’s Corkscrew rule.
(b) Fleming's left-hand rule.
(c) Fleming's right-hand rule.

Question. (a) What are magnetic field lines ? How is the direction of magnetic field at a point in a magnetic field determined using field lines ?
(b) Two circular coils ‘X’ and ‘Y’ are placed close to each other. If the current in the coil ‘X’ is changed, will some current be induced in the coil ‘Y’ ? Give reason.
(c) State ‘Fleming’s right hand rule”.
Answer: (a) A closed continuous curved path around a magnet such that the tangent at any point on the curve gives the direction of magnetic field at that point is called a magnetic field line.
Direction of magnetic field at a point in a magnetic field determined using field lines by drawing a tangent on the magnetic field line at that point.
(b) Yes.
With change in current in the coil X, the magnetic field associated with it also changes around the coil Y placed near it. This change in magnetic field induces a current in the coil Y.
(c) Fleming‘s right hand rule
Stretch the thumb, forefinger and middle finger of right hand so that they are perpendicular to each other. If the forefinger indicates the direction of the magnetic field and the thumb shows the direction of motion of the conductor, then the middle finger will show the direction of induced current in the conductor. This side is also called dynamo rule.

Assertion and Reasoning Based Questions

Directions : In the following questions, a statement of assertion is followed by a statement of reason. Mark the correct choice as :
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true, but reason is not the correct explanation of assertion.
(c) If assertion is true, but reason is false.
(d) If assertion is false but reason is true.

Question. Assertion : A pump operated by electric motor starts pumping liquid.
Reason : Motor converts mechanical energy to electrical energy.
(a) a
(b) b
(c) c
(d) d
Answer: c
Answer: An electric motor converts electrical energy to mechanical energy which is used for pumping liquids through the pumps. It produces a rotating force when electricity is given to it. So, assertion is true, but reason is false.

Question. Assertion : Galvanometer is used to measure polarity.
Reason : Galvanometer is an instrument which is used to detect current in any circuit.
(a) a
(b) b
(c) c
(d) d
Answer: b
Answer: In testing purposes galvanometer is used to measure polarity. There is a torque acting on a current carrying coil suspended in a magnetic field which produces deflection. Deflection is directly proportional to current flowing through the galvanometer coil. Both statements are corrent.

Question. Assertion : Electric generator uses mechanical energy and converts it into electrical energy.
Reason : Electric generator works on the principle of Electromagnetic induction.
(a) a
(b) b
(c) c
(d) d
Answer: a
Answer: The axle of the generator is mechanically rotated to rotate the coil inside the magnetic field. The rotating coil is kept between two poles of a permanent magnet. Due to the electromagnetic induction electricity is produced through the coils. So, both assertion and reason are true and reason is the correct explanation of assertion.

Question. Assertion : A fault occurred in the domestic lines, but all the equipment’s are safe.
Reason : Potential difference is only \( 220\ \text{V} \) in our country in domestic lines.
(a) a
(b) b
(c) c
(d) d
Answer: b
Answer: Both the statements are correct individually, but the reason is not the correct explanation of assertion. As when a fault occurs in the domestic lines there is a protective device called fuse which breaks the circuit and protects all the equipment’s by melting the low melting point wire wrapped to it in order to interrupt supply.

Question. Assertion : Frequency of AC circuits is \( 50\ \text{Hz} \) in India.
Reason : DC is alternating in nature.
(a) a
(b) b
(c) c
(d) d
Answer: c
Answer: In India AC has a tendency to change the direction every 1/100th of a second so the frequency comes to be \( 50\ \text{Hz} \). And AC is alternating in nature whereas DC flows in only one direction. AC can be transmitted to large distances without many losses as compared to DC. thus, assertion is true but the reason is false.

Creating Based Questions

Question. For experimenting purpose, Ram made two electromagnets by wrapping a few turns of wire on one nail and doubled the number of turns of wire for the other nail and let the same amount of electric current passed through it. From his inference, which one tends to have larger magnetic strength ?
Answer: The number of turns of the wire wrapped over the two iron nails is in the ratio of \( 2 : 1 \). Electromagnetic strength has a direct relationship with the number of turns wrapped over it. The strength of electromagnet increases with increase in a number of turns of the wire wrapped over the nail and the current passing through them. Hence, the one with more number of turns tends to have more magnetic strength.

Question. Selena measures the magnetic field produced by an infinitely long wire, a rectangular loop, a solenoid of finite length, a circular loop where all the four carries the same amount of current. After her experiment, she tends to notice that the magnetic field produced by certain cases is similar to the magnetic field produced by the bar magnet. Find out the cases in which both the magnetic fields are equal ?
Answer: Solenoid is the only thing which is tightly-packed in terms of close loops. If current is passed inside a solenoid which is of finite length, the closely packed loops inside it produce a magnetic field which resembles the magnetic field of a bar magnet. Other than this, the circular or rectangular loop doesn’t produce much magnetic field as that of a bar magnet.

Question. Blair wants to measure magnetic field. Suggest her a better instrument which would measure magnetic field approximately.
Answer: Blair can use flux meter to measure the magnetic field since it can be used to predict the flux amount produced in the permanent magnet due to its low controlling torque and its heavy electromagnetic damping. It is better than a ballistic galvanometer since it has high torque and its accuracy is less.

Question. Using the following information form a pathway that defines the working of the electric motor. And also include information that is not mentioned below to complete it. Battery, Horse-shoe magnet, vertical position, Commutator, rectangle coil, Magnetic force, horizontal position.
Answer: Rectangle coil is placed between horse-shoe magnet → Coil is connected to the battery through brush and commutator → The current flow through the coil which is placed between magnetic field → Rectangle coil rotates from the horizontal position → The current stop flowing when the coil attains vertical position because the brush and the commutator ring will not in connection → Though the coil keeps rotates because of the momentum from the earlier rotation → now the coil attains horizontal position → Coil again starts to rotate → With the help of Fleming’s left-hand rule, the direction of the rotation of the coil is determined.

Question. Using the following information form a pathway to determine the direction of the electric current in electric generator. And also include information that is not mentioned below to complete it. Induced electric current, Orthogonal, Magnetic field, Index finger, Middle finger, Thumb, Right - hand.
Answer: We can find the direction of the electric current in the electric generator using Fleming’s right- and rule. This rule is a mnemonics with which we can easily determine the direction of the electric current. In right hand, → Three fingers → Index finger → Middle finger → Thumb → Placed orthogonal position → Thumb defines the direction of the motion of the conductor → Index finger defines the direction of the magnetic field → Middle finger defines the direction of the induced current → Used to find the direction of current in electric generator → Also known as generator rule.