TS 10th Class Physical Science Bits Chapter 10 Electromagnetism

These TS 10th Class Physical Science Bits with Answers Chapter 10 Electromagnetism will help students to enhance their time management skills.

TS 10th Class Physical Science Bits Chapter 10 Electromagnetism

Question 1.
If nduced emf is ‘e’, ΔΦ is change in flux and Dt is time then, mathematical form of’e’is ……………………. . ( )
(A) ΔΦ/t²
(B) Δt/ ΔΦ
(C) ΔΦ × Δt
(D) ΔΦ/Δt
Answer:
(D) ΔΦ/Δt

Question 2.
‘The induced current will appear in such a direction that it opposes the changes in the flux in the coil” …………………. this is called : ( )
(A) Ampere’s swimming rule
(B) Maxwell’s cork screw rule
(C) Lenz’s law
(D) Faraday’s law of magnetic induction
Answer:
(C) Lenz’s law

Question 3.
Right hand rule helps us to find the …………………….. of magnetic force exerted by field on current carrying wire : ( )
(A) magnitude
(B) direction
(C) both A & B
(D) change of emf
Answer:
(B) direction

Question 4.
The magnetic force ‘F’ when direction of electric current is at an angle ‘θ’ to magnetic field Is given by, f = ( )
(A) ILB cos θ
(B) ILB tan θ
(C) ILB sin θ
(D) LLB cot θ
Answer:
(C) ILB sin θ

Question 5.
To increase the speed of an electric motor we have to : ( )
(A) reduce the number of turns of coil
(B) increase the number of turns of coil
(C) increase the current in the coil
(D) both B and C
Answer:
(D) both B and C

Question 6.
The induced current is maximum when the direction of motion of the coil is ……………….. to the magnetic field. ( )
(A) at angle 60°
(B) parallel
(C) at angle 45°
(D) at right angles
Answer:
(D) at right angles

Question 7.
A coil of circular turns of insulated copper wire wrapped closely in the shape of a cylinder is called ( )
(A) rheostat
(B) solenoid
(C) transformer
(D) galvanometer
Answer:
(B) solenoid

Question 8.
Mathematical representation of Faraday’s law of electromagnetic induction is ………………… . ( )
(A) Φ = dE/dt
(B) Φ = -dE/dt
(C) E = dΦ/dt
(D) E = -dΦ/dt
Answer:
(D) E = -dΦ/dt

Question 9.
In starting the engine of an automobile, the work done by the battery is 3000 J and 250 coulombs of charge flows through the motor. The RD. between the terminals of the motor is ……………………… . ( )
(A) 75 V
(B) 18V
(C) 7.5 V
(D) 12 V
Answer:
(D) 12 V

Question 10.
Two electric bulbs A and B are connected in parallel in a circuit produce power of 12 W and 24 W respectively. The ratio of their filament resistances is ………………………… . ( )
(A) 2:1
(B) 1:2
(C) 1:1
(D) 1:3
Answer:
(A) 2:1

Question 11.
Lenz’s law does not violate the principle of ( )
(A) conservation of energy
(B) conservation of charge
(C) conservation of mass
(D) conservation of momentum
Answer:
(A) conservation of energy

Question 12.
If ’A’ is the area through which a flux f passes normally, then the magnetic flux density B Is given by ( )
(A)B=Q/A²
(B) B=QA
(C) B=Q/A³
(D) B=Q/A
Answer:
(D) B=Q/A

Question 13.
The unit of consumption of electrical energy in houses is ‘unlt It means ……………. .( )
(A) kilo-watt-hour
(B) joule-hour
(C) kilo joule
(D) mega watt
Answer:
(A) kilo-watt-hour

Question 14.
The unit commonly used to measure work done ( )
(A) ampere
(B) watt
(C) joule
(D) calorie
Answer:
(C) joule

Question 15.
There are ten 60w. bulbs in a house. If all G cnem arc hghted for 5 hours a day, the expenditure in a month of 30 days at ₹4.00 per unit is ……………… . ( )
(A) ₹ 36
(B) ₹ 360
(C) ₹ 3.60
(D) ₹ 72
Answer:
(B) ₹ 360

Question 16.
A.C. changes direction after every ( )
(A) 1/10th second
(B) 1/100th second
(C) 1/1000th second
(D) 0.1th second
Answer:
(B) 1/100th second

Question 17.
A rectangular coil of copper wire is rotated In a magnetic field. The direction of the induced current changes once in each: ( )
(A) 2 revolutions
(B) one revolution
(C) half revolution
(D) 1/4th revolution
Answer:
(C) half revolution

Question 18.
The neutral wire is usually covered with : ( )
(A) green insulation
(B) red insulation
(C) black insulation
(D) blue insulation
Answer:
(C) black insulation

Question 19.
A current which changes direction after equal intervals of time is abbreviated as ( )
(A) A.C.
(B) D.C.
(C) F.C.
(D) I.C.
Answer:
(A) A.C.

Question 20.
When the live wire and neutral wire come into direct contact, It may cause ( )
(A) over loading
(B) low current
(C) direct current
(D) none of these
Answer:
(A) overloading

Question 21.
This works on the principle of electro-magnetic induction: ( )
(A) motor
(B) computer
(C) cell phone
(D) generator
Answer:
(D) generator

Question 22.
The process by which a changing magnetic field in a conductor induces a current in another conductor Is called ………………………. . ( )
(A) magnetic field induction
(B) electromagnetic induction
(C) chemical effect
(D) joule’s effect
Answer:
(B) electromagnetic induction

Question 23.
The direction of current Induced in a conductor in right-hand thumb rule is given by ( )
(A) index finger
(B) thumb
(C) middle finger
(D) little finger
Answer:
(C) middle finger

Question 24.
Two metallic half rings form the ………………………….. of an electric motor. ( )
(A) commutator
(B) axis
(C) armature
(D) rheostat
Answer:
(A) commutator

Question 25.
A stationary magnetic field is provided in a generator by ( )
(A) permanent horse-shoe magnet
(B) solenoid
(C) electromagnet
(D) ring-shaped magnet
Answer:
(A) permanent horse-shoe magnet

Question 26.
The rate of electrical work done is called – ( )
(A) electric potential
(B) electric power
(C) mechanical equivalent
(D) electrochemical equivalent
Answer:
(B) electric power

Question 27.
In a non-uniform magnetic field the net field in upper part of rotating coil is ( )
(A) weak
(B) average
(C) low
(D) strong
Answer:
(D) strong

Question 28.
This depends on the orientation of plane in the field : ( )
(A) magnetic flux
(B) magnetic induction
(C) strength of emf
(D) pole strength
Answer:
(B) magnetic induction

Question 29.
If V₀ be the value of A.C. emf, then V_rms = ( )
(A) V₀/2
(B) \(\sqrt{2}\) V₀
(C) \(\frac{2}{v_0}\)
(D) \(\mathrm{v}_0 \sqrt{2}\)
Answer:
(D) \(\mathrm{v}_0 \sqrt{2}\)

Question 30.
Electric power – P = ( )
(A) IΔt/ ΔΦ
(B) i²Δt /ΔΦ
(C) IΔt/Δt
(D) IΔΦ/Δt
Answer:
(D) IΔΦ/Δt

Question 31.
A quantity that has both direction and magnitude is ( )
(A) speed
(B) temperature
(C) electric current
(D) magnetic field
Answer:
(D) magnetic field

Question 32.
The total equal and opposite forces acting on the metal cap of a cool drink bottle when we turn It constitute ( )
(A) concurrent forces
(B) couple
(C) coincident forces
(D) attracting forces
Answer:
(B) couple

Question 33.
In the formula F=qvB, the letter ‘q’ stands for ( )
(A) flux density
(B) repulsive force
(C) charge
(D) velocity of charge
Answer:
(C) charge

Question 34.
The direction of magnetic field due to coil points towards you when the current in the coil is in ………………………. . ( )
(A) positive direction
(B) south direction
(C) anti-clockwise direction
(D) clockwise direction
Answer:
(C) anti-clockwise direction

Question 35.
When a conductor of length 1’ moves perpendicular to field ‘B’ with a speed ‘V’, then potential difference developed between the ends of the conductor is ( )
(A) BV
(B) B/V
(C) B/V²
(D) B²/V
Answer:
(B) B/V

Question 36.
To increase the speed of an electric motor. ( )
(A) reduce the number of turns in the coil
(B) increase the number of turns In the coil
(C) increase the current
(D) Both B&C
Answer:
(D) Both B&C

Question 37.
An electric motor working on A.C. does not require : ( )
(A) brushes
(B) commutator
(C) shaft
(D) electromagnet
Answer:
(B) commutator

Question 38.
The field lines in a magnetic field appear to be: ( )
(A) closed ellipses
(B) closed loops
(C) open loops
(D) closed hyperbolas
Answer:
(B) closed loops

Question 39.
The flux through the plane is given by, f = ( )
(A) BA sinθ
(B) BA tanθ
(C) BA cosθ
(D) BA/sinθ
Answer:
(C) BA cosθ

Question 40.
Magnetic flux density B = ( )
(A) Magnetic flux / Effective area
(B) Effective area I Magnetic flux
(C) Strength of field / Length of magnet
(D) Magnetic moment / Effective area
Answer:
(A) Magnetic flux / Effective area

Question 41.
Current carrying wire produces ( )
(A) charge
(B) magnetic field
(C) lightning
(D) none of these
Answer:
(B) magnetic field

Question 42.
The statement current is defined as rate of flow of electrons through any cross-section: – Is this ( )
(A) always true?
(B) always false?
(C) true in some cases
(D) none of these
Answer:
(C) true in some cases

Question 43.
Volt – ampere = ( )
(A) Watt
(B) Newton
(C) Farad
(D) Henry
Answer:
(A) Watt

Question 44.
A rectangular coil of wire, a soft iron core together constituted the ………………….. of an electric motor. ( )
(A) shaft
(B) commutator
(C) armature
(D) brushes
Answer:
(C) armature

Question 45.
The change in the magnetic flux in the cause of ( )
(A) induced magnetic moment
(B) Induced emf
(C) increase in resistance
(D) production chemical energy
Answer:
(B) Induced emf

Question 46.
The resulting magnetic lines of force formed around a straight conductor carrying a current are ……………………….. . ( )
(A) intersecting circles
(B) non Intersecting circles
(C) circles touching each other
(D) concentric circles
Answer:
(D) concentric circles

Question 47.
One of the factors that Increase the speed of an electric motor ( )
(A) area of armature
(B) thickness of shaft
(C) material armature
(D) none of these
Answer:
(A) area of armature

Question 48.
The law of electro magnetic induction was proposed by – ( )
(A) Lenz
(B) Fleming
(C) Ampere
(D) Faraday
Answer:
(D) Faraday

Question 49.
A magnet is pulled away from a conducting coil in a circuit. The direction of the induced emf. in the coil can be found from: ( )
(A) Faraday’s law of electromagnetic induction
(B) Joule’s law
(C) Lenz’s law
(D) Fleming’s left-hand rule
Answer:
(A) Faraday’s law of electromagnetic induction

Question 50.
An electric motor that works on D.C. requires : ( )
(A) shaft
(B) iron core
(C) commutator
(D) all
Answer:
(D) all

Question 51.
Current enters Into an electric motor through : ( )
(A) Call
(B) Brush and a half ring
(C) shaft
(D) armature
Answer:
(B) Brush and a half ring

Question 52.
In Fleming’s right-hand rule the finger that shows the direction of induced current is ( )
(A) middle finger
(B) thumb
(C) fore linger
(D) little finger
Answer:
(A) middle finger

Question 53.
When the current in the coil is in clockwise direction, the direction of magnetic field In coil points …………………. from you. ( )
(A) away
(B) towards
(C) towards right hand
(D) none of these
Answer:
(A) away

Question 54.
An appliance that works on the principle of electro-magnetic induction is ( )
(A) solar cooker
(B) LPG stove
(C) induction stove
(D) Wicks stove
Answer:
(C) induction stove

Question 55.
The magnetic effect of current was discovered by ( )
(A) Faraday
(B) Henry
(C) Oersted
(D) Maxwell
Answer:
(C) Oersted

Question 56.
Electromagnetic induction is involved in ( )
(A) charging a body with positive charge
(B) production of current by relative motion between magnet and the coil
(C) rotation of the coil of an electric motor
(D) generation of magnetic field due to a current
Answer:
(B) production of current by relative motion between magnet and the coil

Question 57.
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 58.
Current carrying conductor placed in a magnetic field experiences a force. The device based on thfs principle is ( )
(A) electrical generator
(B) electric motor
(C) electric bell
(D) none of these
Answer:
(B) electric motor

Question 59.
A current is flowing in a circular loop of wire In clockwise direction. The magnetic field at the centre of the loop is ( )
(A) directed downward
(B) zero
(C) inversely proportional to the radius of the loop
(D) directed upward
Answer:
(A) directed downward

Question 60.
The device used for producing electric current is called a ( )
(A) generator
(B) galvanometer
(C) ammeter
(D) motor
Answer:
(A) generator

Question 61.
The effective length of the magnet is ( )
(A) the complete length of the magnet
(B) the distance between the two poles of the magnet
(C) the half of the length of the magnet
(D) the square of the length of the magnet
Answer:
(B) the distance between the two poles of the magnet

Question 62.
The conductivity of a magnetic substance for the lines of force with respect to air is called the ( )
(A) Magnetic Induction
(B) Magnetic permeability
(C) Magnetic flux density
(D) Intensity of magnetization
Answer:
(B) Magnetic permeability

Question 63.
The magnetic flux is expressed in ( )
(A) Dynes
(B) Oersted
(C) Gauss
(D) Weber
Answer:
(D) Weber

Question 64.
The magnetic lines of force, Inside a current-carrying solenoid, are ( )
(A) along the axis and are parallel to each other
(B) perpendicular to the axis and equidistance from each other
(C) circular and they do not intersect each other
(D) circular at the ends but they are parallel to the axis inside the solenoid
Answer:
(A) along the axis and are parallel to each other

Question 65.
The vertical component of the earths magnetic field is ( )
(A) zero at the magnetic pole
(B) zero at the geographic pole
(C) same everywhere
(D) zero at the magnetic equator
Answer:
(D) zero at the magnetic equator

Question 66.
A current-carrying loop lying in a magnetic field behaves like a ( )
(A) a magnetic dipole
(B) magnetic pole
(C) magnetic material
(D) non-magnetic material
Answer:
(A) a magnetic dipole

Question 67.
Power factor is one for ( )
(A) pure inductor
(B) pure capacitor
(C) pure resistor
(D) either an inductor or a capacitor
Answer:
(C) pure resistor

Question 68.
The AC voltage across a resistance can be measured using ( )
(A) a potentiometer
(B) a hot-wire voltmeter
(C) a moving-coil galvanometer
(D) a moving-magnet galvanometer
Answer:
(B) a hot-wire voltmeter

Question 69.
The essential difference between an AC generator and a DC generator is that ( )
(A) AC generator has an electromagnet while a DC generator has permanent magnet
(B) DC generator will generate a higher voltage
(C) AC generator will generate a higher voltage
(D) AC generator has slip nngs while the DC generator has a commutator
Answer:
(D) AC generator has slip rings while the DC generator has a commutator

Question 70.
At the time of short circuit, the current in the circuit ( )
(A) reduces substantially
(B) does not change
(C) increase heavily
(D) vary continuously
Answer:
(C) increase heavily

Question 71.
The current n a generator armature is AC because ( )
(A) The magnetic field reverses at Intervals
(B) the current in the field coils is AC
(C) the rotation of the armature causes the field through it to reverse
(D) the commutator feeds current into ¡t in opposite directions every half cycle
Answer:
(C) the rotation of the armature causes the field through it to reverse

Question 72.
A DC generator is based on the principle of ( )
(A) magnetic effect of current
(B) heating effect of current
(C) energy dissipation
(D) electromagnetic conduction
Answer:
(D) electromagnetic conduction

Question 73.
For making strong electromagnet, the material of the core should be ( )
(A) brass
(B) laminated steel strips
(C) soft iron
(D) steel
Answer:
(C) soft iron

Question 74.
A soft iron bar is introduced Inside a current carrying solenoid. The magnetic field inside the solenoid ( )
(A) will increase
(B) will remain unaffected
(C) will become zero
(D) will decrease
Answer:
(A) will increase

Question 75.
A rectangular coil of copper wire is rotated in a magnetic field. The direction of the induced current changes once in each. ( )
(A) one revolution
(B) one fourth revolution
(C) half revolution
(D) two revolutions
Answer:
(B) one fourth revolution

Question 76.
The frequency of direct current is ( )
(A) zero
(B) 50 Hz
(C) 60 Hz
(D) 100 Hz
Answer:
(A) zero

Question 77.
Who invented electric generator? ( )
(A) Oersted
(B) Coulomb
(C) Rutherford
(D) Michael Faraday
Answer:
(D) Michael Faraday

Question 78.
Magnetic flux is the product of magnetic field induction and ……………………….. . ( )
(A) magnetic moment
(B) area
(C) magnetic intensity
(D) resistance
Answer:
(B) area

Question 79.
A current-carrying wire of length L is placed perpendicular to a uniform magnetic field B. Then the force acting on the wire with current I is …………………….. . ( )
(A) F = Bi
(B) F = Bl
(C) B = iF
(D) F = Bil
Answer:
(D) F = Bil

Question 80.
The magnetic field inside a ………………… is uniform. ( )
(A) current carrying conductor
(B) solenoid
(C) coil
(D) magnet
Answer:
(D) magnet

Question 81.
An AC generator ¡s provided with ………………………. slip rings which rotate with the coil. ( )
(A) one
(B) three
(C) two
(D) four
Answer:
(C) two

Question 82.
The moving part of the electnc motor is called ………………………. . ( )
(A) magnets
(B) shaft
(C) armature
(D) carbon brushes
Answer:
(B) shaft

Question 83.
SI unit of magnetic field strength is ……………….. . ( )
(A) tesla
(B) weber
(C) amp/m²
(D) volt
Answer:
(A) tesla

Question 84.
The laws of induction were given by ( )
(A) Faraday
(B) Kirchoff
(C) Lenz
(D) Lorenz
Answer:
(C) Lenz

Question 85.
The energy resides ¡n a current carrying inductor In the form of …………………….. . ( )
(A) resistance
(B) heat
(C) magnetic field
(D) thermal energy
Answer:
(C) magnetic field

Question 86.
The direction of motion of a conductor, kept in a magnetic field is given by ………………… . ( )
(A) Kirchoffs rule
(B) Lenz’s law
(C) Flemimng’s left hand rule
(D) Flemming’s right hand rule
Answer:
(C) Flemimng’s left hand rule

Question 87.
Which of the following consists soft iron core ? ( )
(A) electric generator
(B) solenoid
(C) dynamo
(D) electnc motor
Answer:
(B) solenoid

Question 88.
The direction of induced emf as indicated by ( )
(A) Lenz’s law
(B) Fleming’s right hand rule
(C) both 1&2
(D) none of these
Answer:
(C) both 1&2

Question 89.
The principle on which a generator works is ( )
(A) Fleming’s right hand rule
(B) Joule’s law
(C) Maxwell’s cork screw rule
(D) Ampere’s swimming rule
Answer:
(A) Fleming’s right hand rule

Question 90.
In fleming’s left hand rule, the finger that indicates the direction of motion of coil is ……………… . ( )
(A) middle finger
(B) thumb
(C) index finger
(D) little finger
Answer:
(B) thumb

Question 91.
The instrument used In our daily life to convert the electrical energy into mechanical energy is …………………. . ( )
(A) Electric bulb
(B) Electric motor
(C) Generator
(D) Induction stove
Answer:
(B) Electric motor