Science MCQ

charge

the magnetic effect of electric current

Electric current

1.2 V

2 V

The symbol shown in the figure represents a tapping key and a switch respectively.
Tapping key: a light flexible metallic strip provided with contacts so that when it is momentarily pressed an electric circuit is made or broken and when it is released the opposite effect is automatically produced.
Switch: a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another.

Electric wire.

When the swithch of electrical bell push, circuit will complete and current will start to flow.

The batteries used in tractors, trucks are also made from cells.

The given symbol is for transformer in electric circuit.

When a current passes through an electric heater, it becomes very hot and becomes a source of heat.
Therefore, in an electric heater, electrical energy is converted into heat energy.

The switch is a simple device that is used to either break the electric circuit or to complete it.

Closed.

When the switch is pressed, the circuit completes and ringing begins.
Hence, electrical energy is converted to sound energy.
As the switch is released, no current flows, and no energy is consumed.

An electric room heater or an electric heater used for cooking contains a coil of wire.
The coil of wire used in electric heaters is called a heating element.

Electric bulb.

The positive terminal of one cell is connected to the negative terminal.

A common dry cell used in torches consists of a rod surrounded by a chemical paste in a metal case.

The key or Switch can be placed anywhere in the electric circuit.

The marked ‘ is called the negative terminal.

When an electric current flows through a wire, it behaves like a magnet. „
A current carrying coil of an insulated wire wrapped around a piece of iron is called an electromagnet.
The electromagnets are also used to separate magnetic material from the junk.

Wires, cells, switches, bulbs are element of a circuit.

Without the flexibility strip, the striker will not come back to original position when the electrical circuit breaks.

A switch is a device that is used for making and breaking electric current in a circuit.
It is used to turn on and turn off daily used equipment like television, washing machine, fan, light, etc.

Negative.

Connecting wires.

Combination of two or more cells is called battery.

An electromagnet is a coil of insulated wire.

Two or more cells.

A fan uses electric current to rotate to blow air.

Increasing the number of turns in the solenoid.

Oersted.

The electric iron, electric heater and electric bulb are some of the familiar devices based on Joule’s Law, but electric fan is not based on Joule's Law.

Heating effect of current.

The bulb glows only when current flows through the circuit and current heats the filament of bulb and bulb gives light.

The magnetic material around the coil is wound is core.

At a high temperature.

Rheostat is a variable resistor, which is used to control the flow of electric current by manually increasing or decreasing the resistance.
The arrow sign indicates the variability.

Greater.

Soft iron is used for making the armature of an electric bell because we don't want the armature to retain its magnetism when the current is withdrawn. 
Soft iron is magnetised easily on passing the current and completely demagnetised easily on withdrawing the current through the solenoid. 

An electric bell is a mechanical or electronic bell that functions by means of an electromagnet.
When an electric current is applied, it produces a repetitive buzzing, clanging or ringing sound.

A rheostat is a variable resistor which is used to control current.
they are able to vary the resistance in circuit without interruption.
the construction of a rheostat is very similar to potentiometer.
Thus A rheostat is used in circuit to change the resistance of the circuit.

Ohm.

Hans Christian Oersted.

The positive terminal of one cell is connected to the negative terminal of the next cell.
Such a combination is called a battery.

Iron.

Fuse is a device used to prevent overheating of appliances due to a sudden increase in the current in the circuit.
It protects the device and the user.
When the electric current is higher than the normal current needed by a circuit, the fuse blows up and breaks the circuit.
Hence, it protects the circuit from a power overload.

The working of an electric magnet is based on the magnetic effect of current.
When the key is pressed the circuit gets completed and current passes through it causing the electromagnet to get magnetized which in turn attracts the armature.
This movement of the armature causes the hammer to strike the gong.

Very strong electromagnet is used for lifting iron pieces.

Striker always repeatedly hits metal gong.

Electrical energy is converted into sound energy.

Fuse.

Electromagnets are formed by passing an electric current through a wire coiled around the substance with iron core.
Electromagnets are used to speaker, motor and generator.

Melted away.

Electrical energy is caused by moving electric charges called electrons.
The faster the charges move, the more electrical energy they carry.
As the charges that cause the energy are moving, electrical energy is a form of kinetic energy.

Allowed to flow through.

Electric bell works on the mechanism of electromagnets i.e, temporary magnets, and no permanent magnet is used.
Temporary magnet allows the ferromagnetic strip to return back to its initial state as switch is released.

A fuse is an automatic means of removing power from a faulty system.
So, metals with low melting point and high resistance are used to make a fuse wire.
Therefore, tin or tin - lead alloy whose melting point is low will be used in making fuse wire.

An electric bell is a mechanical or electronic bell that functions by means of an electromagnet.
When an electric current is applied, it produces a repetitive buzzing, clanging or ringing sound. 
The material used for making the armature of an electric bell is soft iron which can induce magnetism rapidly.
Hence it can serve as a good electromagnet.

Electromagnets are formed by the wounding of conducting wires like coil over the soft iron core.

Fuse is a safety device that cuts off the current.

An electric bell is a mechanical or electronic bell that functions by means of an electromagnet.
When an electric current is applied, it produces a repetitive buzzing, clanging or ringing sound.
So clearly the electrical energy is converting into sound energy.

An electromagnet is employed in an electric bell.
When the push button is pressed the electric circuit is completed and the armature is attracted towards the electromagnet.
As a result, the small spring gets detached from the screw due to which the electric circuit is broken and the electromagnet is demagnetized.
Hence, the attraction disappears and the armature is brought back by the spring to its original position.
Contact of the spring with the screw is now remade, which completes the electric circuit.
The action is repeated over and over again continuously.
The armature vibrates and the hammer attached to it strikes the gong and the bell rings and sound is produced.

A circuit diagram represent on electrical circuit.

In order to make a battery the positive terminal of one cell is connected to the negative terminal of the other cell.

An electric bell is a mechanical or electronic bell that functions by means of an electromagnet.
When an electric current flows through the coils, the electromagnet creates a magnetic field which pulls the armature towards it, causing the hammer to strike the bell.

The ammeter is used to measure, the rate at which the electrons flow through the globes and the voltmeter measures the potential drop that is actually the loss in potential energy as the electricity moves through the filament.

The given picture is of a resistance.

The given symbol is switch.
Used in the electric circuits.
An electric switch is a device that interrupts the electron flow in a circuit.
Switches are primarily binary devices: either fully on or off and light switches have a simple design.
When the switch is turned off, the circuit breaks, and the power flow is interrupted.
Circuits consist of a source of power and load.

Resistor is not a circuit element.

Torches
Transistors, toys
T.V remote controls
All of these use batteries.

Element.

The shorter, thicker vertical line in the symbol of a cell represents the negative terminal.
The longer, thinner vertical line in the symbol of a cell represents the positive terminal.

As the current in coil flows due to electromagnetism, it behaves as magnet then the elementary magnets of soft iron core get attracted and on stopping current elementary magnets lose alignment.

When a conductor carrying current is placed perpendicular to the direction of magnetic field, the force acting on it is given by Fleming's left hand rule. Since the direction of current is the same as that of the motion of a positive charge, the direction of force acting on it when moving perpendicular to the direction of magnetic field is the same as that acting on a current-carrying conductor placed perpendicular to the direction of magnetic field. Obviously, the force acting on an electron is opposite to that. Therefore in this case it is into the page.

A Battery.

Tungsten is a poor conductor of electricity even though it is a metal.
But at high temperatures, it will conduct electricity.
As discussed above, it has a high melting point.
Therefore, high temperature doesn't have any bad effect on Tungsten.

A resistor is an instrument which provides a resistance to the flow of current.
Electric energy to the circuit is provided by a battery.

A conductor allows the flow of electrons through itself that produces electric current.
But conductors also resist the flow of electrons to some extent.
When electron flow is restricted, some of the energy of electrons is converted to heat energy instead of electrical energy.

Electromagnets are temporary magnets that have the property of a magnetic only when they are connected to an electrical source.

Nails is conductor of electricity.

When the electric circuit is completed the electromagnet is activated and the soft iron armature is strongly pulled.
The hammer strikes the gong producing the sound.
So, the magnetic force  is responsible for the movement of hammer.

Iron.

Room heater does not use an electro magnet.

Magnetic effect of current.

None of these Liquid is bad conductor of electricity. A circuit diagram represent on electrical circuit.

The given symbol is the symbol of the Electric bulb used in a circuit diagram.

An electric bell contains an electromagnet, consisting of coils of insulated wire wound round iron rods.
When an electric current flows through the coils, the rods become magnetic and attract a piece of iron attached to a clapper.
The clapper hits the bell and makes it ring.

The bulb has thin wire called filament.

The bell works on the principle of electromagnetism which says that when an electric current flows through the coil, the rods become magnetic and attract a piece of iron attached to a clapper.
And the clapper hits the cap and comes back as the current stops, and hence the bell rings.
 So the current flows and stops in succession.
And in this way the bell rings.

Electrical symbol of cell, resistor, conducting wire and cell are shown in the figure.
Thus a straight line in an electrical circuit represents a conducting wire.

A solenoid is a cylindrical coil of wire.

To control a device

Heating appliances generally contain coils of high resistance wire made of nichrome alloy.
When these appliances are connected to power supply by insulated copper wires then a large amount of heat is produced in the heating coils because they have high resistance.

Open circuit is broken at some point.

The symbol in the above figure represents an alternating current source.

Make and break arrangement causes the striker to repeatedly hit the metal gong as long as the switch is pressed.
When the circuit is complete, electromagnet attracts the striker which hits metal gong.
As soon as the striker moves, circuit breaks and electromagnet is inactive.
Because of flexibility of striker, it moves back to its original position.
As soon as it reaches original position, the circuit is complete.
This process repeats continuously as long as the switch remains pressed. 

Switch.

A battery is a combination of two or more cells connected end to end such that positive terminal of one cell is connected to negative terminal of next cell.

The working of an electric bell is based on the magnetic effect of current.
When the key is pressed, the circuit gets completed and current passes through it causing the electromagnet to get magnetised which in turn attracts the armature.
This movement of the armature causes the hammer to strike the gong. 
However when the armature moves towards the gong the connection between the spring strip and adjusting screw is lost which breaks the circuit and the current flow is stopped thus demagnetising the electromagnet.
This causes the armature to return to its original position and it is thus pulled back due to the spring effect of the spring strip.
This process is called a make and break circuit.

Always fuse breaks on shorting of wire and flowing exessive current.

Glowing electric bulbs becomes warm due to the heating effect of electric current.
The current flowing through the filament of the bulb heats up the filament due to Joules heating and the bulb glows.
The heat that is responsible for the production of light in the filament heats up the bulb.

The working of an electric magnet is based on the magnetic effect of the current.
When the key is pressed the circuit gets completed and current passes through it causing the electromagnet to get magnetized which in turn attracts the armature.
This movement of the armature causes the hammer to strike the gong.
However, when the armature moves towards the gong the connection between the spring strip and adjusting screw is lost which breaks the circuit, and the current flow is stopped thus demagnetizing the electromagnet.
This causes the armature to return to its original position and it is thus pulled back due to the spring effect of the spring strip.
This process is called a make and brake circuit.

When electric current passes through the filaments of the bulb, it starts emitting light due to the heating effect of the electric current.
Most of the power consumed by the filament appears as heat, but a small part of it is in the form of light which is radiated through the filamaent.

Bar magnet.

Closed.

All the bulbs will glow simultaneously because there is no time lag in the flow of current as soon as the circuit is complete.

Striker is attracted to the electromagnet when circuit is complete.
When external magnetic field perpendicular to motion of striker is applied no effect is produced in the functioning.
The reason for above is that motion of striker is hindered mechanically in that direction.

In case of electric fuse, there is only a maximum limit on the current which can safely flow in the electric circuits.

It deflects a magnetic needle placed near it because a magnetic field is created when the current passes through it.