An electromagnet consists of a long coil of insulated copper wire wound on a soft:
1.Aluminium core
2.Silver core
3.Zinc core
4. Iron core
At what time interval does the alternating current produced in India reverse its direction?
1. 1/100 second
2. 5 seconds
3. 1 minute
4.5 minutes
 Magnitude of current induced in the coil can be increased by increasing:
1.Number of coil turns
2. Strength of magnet
3.Speed of coil rotation
4.All of the above
 The direction of deflection of a current-carrying conductor indicates the direction of:
1.Electric current
2.Force acting on it
3. Magnetic field
4.All of the above
 The production of electric current by moving a magnet inside a fixed coil of wire is a case of:
1.Electromagnetism
2.Electromagnetic induction
3. Making permanent magnet
4.None of the above
 What is the frequency of alternating current produced in India?
1.15 Hz
2.50 Hz
3.55 Hz
4.65 Hz
 Which metal wire is used in the coil of the motor used commercially?
1.Aluminium
2.Silver
3.Nickel
4.Copper
 Which of the following are sources of direct current?
1.Dry cell
2.Car battery
3.D.C. generator
4.All of the above
If the current reverses direction after equal intervals of time, it is called:
1.Direct current
2.Alternating current
3.Induced current
4. Ionic current
In an electric motor, which device reverses the direction of current through a circuit?
1.Carbon brush
2.Coil
3. Commutator
4.Permanent magnet
In generators, the voltage produced can be increased by:
1.Coil with more turns
2.Rotating coil faster
3. Using coil with larger area
4. All of the above
In which of the following devices is the electrical motor used?
1.Electric fans
2.Washing machine
3.Refrigerator
4.All of the above
What is a long coil containing a large number of close turns of insulated copper wire called?
1. Straight
2. Solenoid
3.Circular loop
4.Stranded
On what does the strength of magnetic field produced by a current carrying solenoid depend?
1.Number of turns in solenoid
2.Strength of current
3.Nature of core material
4.All of the above
Strong permanent magnets are used in:
1.Microphones
2.Loudspeakers
3.Voltmeters
4. All of the above
The carbon strips used to pass electric current to the coil are known:
1.Commutator
2.Magnet
3. Battery
4.Brushes
The current produced by moving a straight wire in a magnetic field is called:
1. Direct current
2.Alternating current
3. Induced current
4.Electromagnetism
The magnetic field lines inside the solenoid are:
1. Concentrated circles
2.Bigger circles
3.Parallel straight lines
4.None of the above
The magnetic field produced by a current carrying solenoid is similar to the magnetic field produced by a:
1.Bar magnet
2.Ring magnet
3.Rod magnet
4.Horse shoe magnet
The maximum force is exerted on a current carrying conductor when it is:
1.Perpendicular to magnetic field
2.Parallel to magnetic field
3.Swings in backward direction
4. All of the above
The process of electromagnetic induction has led to the construction of:
1.Motors
2.Generators
3.Transformers
4. Switch
The production of electricity from magnetism is called:
1.Electromagnetic induction
2.Electromagnetism
3.Electroluminescent wire
4.Electrostatics
What does the forefinger represent in the Fleming’s left-hand rule?
1.Magnetic field
2. Current
3.Motion of conductor
4.None of the above
What is the current flowing in one direction called?
1.Alternating current
2.Induced current
3.Direct current
4.Ionic current
What is used to make electromagnets?
1. Circular wire
2.Solenoid
3.Straight wire
4.Horse shoe magnet
What needs to be reversed in order to reverse the direction of induced current?
1.Direction of magnetic field
2.Direction of current
3.Direction of force
4. All of the above
Which are the two main organs of the human body where the magnetic field produced is significant?
1.Heart and kidney
2. Lungs and kidney
3. Heart and brain
4.Liver and stomach
Which device converts electrical energy into mechanical energy?
1.Motor
2.Generator
3.Windmill
4.Transformer
Which direction is indicated by the thumb in Fleming’s left-hand rule?
1.Current
2.Magnetic field
3.Motion of conductor
4.None of the above
Which effect of current is used in detecting concealed current-carrying conductor in a wall?
1.Magnetic
2.Heating
3.Chemical
4. Ionic
Which of the following are the sources for producing alternating current?
1. Power house generators
2.Bicycle dynamos
3.Car alternators
4.All of the above
Which of the following convert’s mechanical energy into electrical energy?
1.Refrigerator
2.Fan
3.Electric motor
4. Electric generator
Which of the following factors affects the strength of steel?
1.Number of turns in coil
2.Current flowing in coil
3.Length of air gap between poles
4.All of the above
Which of the following is not used for making electromagnets?
1.Carbon steel
2.Alnico
3. Cobalt steel
4.All of the above
Which of the following parts is not there in A.C. generator?
1. Slip rings
2.Coil
3.Commutator
4. Galvanometer
Which of the following parts of the generators is stationary to produce electricity in large powerhouses?
1.Coil
2.Electromagnet
3.Slip rings
4.Carbon brush
Which rule is applied to find the direction of force acting on the current-carrying conductor, if the direction of current and direction of magnetic field is known?
1.Maxwell’s right-hand thumb rule
2.Born rule
3.Hall Effect
4.Fleming’s left-hand rule
Who discovered that when a current carrying conductor is placed in a magnetic field, a mechanical force exerted on the conductor makes it move?
1. Hans Christian Oersted
2.Michael Faraday
3.Benjamin Franklin
4.William Gilbert
Who discovered the phenomenon of electromagnetic induction?
1.Michael Faraday and Joseph Henry
2.Albert Einstein
3.Isaac Newton
4.Galileo Galilei