Magnetic Field and Current Quiz

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Questions and Answers

What happens when same poles of two magnets are brought close to each other?

They align

They oscillate

They repel each other (correct)

They attract each other

How does the strength of a magnetic field change as you move away from the magnet?

It remains constant

It increases

It decreases (correct)

It flips direction

What is the direction of the magnetic field at any point between North and South poles?

Points towards both poles

Points away from South pole and towards North pole

Points away from both poles

Points away from North pole and towards South pole (correct)

What happens when induced magnets are 'stroked' with a permanent magnet?

They become permanent magnets Signup and view all the answers

Why does a freely suspended compass align itself with Earth's magnetic field lines?

Because the compass is a bar magnet Signup and view all the answers

'Plotting Compasses' are used to determine what about a magnetic field?

Strength at different distances Signup and view all the answers

What happens when a current flows through a conductor?

The conductor generates its own magnetic field. Signup and view all the answers

How is direct current (DC) produced in a dynamo?

By using split ring commutator to reverse the current. Signup and view all the answers

What happens when more coils are added to the secondary wire of a transformer?

Voltage will increase. Signup and view all the answers

In an alternator, what type of current is typically produced?

Alternating current (AC) Signup and view all the answers

What effect does cutting through a stronger magnetic field have on induced potential difference?

It increases the induced potential difference. Signup and view all the answers

How does a step-down transformer function?

By decreasing voltage while increasing current. Signup and view all the answers

What is the shape of the magnetic field around a wire?

Circular Signup and view all the answers

According to the 'right hand grip rule', what does the current produce around a wire?

Magnetic field Signup and view all the answers

How does the strength of the magnetic field change with distance from the wire?

Weaker Signup and view all the answers

What effect does coiling a wire to form a solenoid have on the magnetic field?

It aligns and strengthens the magnetic field Signup and view all the answers

What factor does NOT affect the strength of a magnetic field around a wire?

Temperature of wire Signup and view all the answers

In electromagnetic induction, what induces a potential difference across a conductor?

Relative movement between conductor and magnetic field Signup and view all the answers

Why does having an iron core in the center of a solenoid increase its magnetic strength?

It aligns and enhances the magnetic effect Signup and view all the answers

What rule can be used to determine the direction of force felt by a wire in a magnetic field?

Fleming's Left Hand Rule Signup and view all the answers

Study Notes

Magnetic Fields and Electromagnetism

A current-carrying wire produces a magnetic field around it, with the direction dictated by the "right-hand grip rule".
The strength of the magnetic field is greater with a higher current and weaker with a greater distance from the wire.

Solenoids

A solenoid has a magnetic field shape similar to a bar magnet.
The magnetic field is enhanced by coiling the wire, causing the field to align and form a single giant field.
Adding an iron core to the centre increases the strength of the magnetic field.
Factors that affect the strength of the magnetic field include the size of the current, length, cross-sectional area, number of turns, and the use of a soft iron core.

The Motor Effect

A magnet and a wire will interact, exerting a force on each other due to the interaction of their magnetic fields.
The magnetic field around a wire is circular, while the magnetic field between two magnets is straight.
When the two fields interact, the wire is pushed away from the field between the poles, at right angles to the wire direction and the field direction.

Fleming's Left Hand Rule

The rule is used to work out the unknown factor (usually the direction of the force felt) out of the three given factors (current direction, magnetic field direction, and force direction).
The directions are 90° to each other.
The rule is used to determine the direction of the force felt on the wire.

Electric Motors

Electric motors work by using a permanent magnet and a coil of current-carrying wire on an axis.
The force on one side of the coil moves it up, while the force on the other side (where the current is flowing in the opposite direction) moves it down.
This creates a rotation, which can be verified using Fleming's Left Hand Rule.

Electromagnetic Induction

When there is a relative movement between a conductor and a magnetic field, a potential difference is induced across the conductor.
The movement of a coil of wire through a magnetic field induces an electromotive force (EMF) in the coil.

Magnets

Magnets have north and south poles, with same poles repelling and opposite poles attracting.
Permanent magnets always have poles, while induced magnets are materials that can be made temporarily magnetic by "stroking" them with a permanent magnet.

Magnetic Fields and the Earth's Core

The Earth's core is magnetic, creating a large magnetic field around the Earth.
The Earth's magnetic field is not aligned with the Geographic North Pole, but rather is located over North Canada.
The Earth's magnetic pole above Canada is actually a magnetic South Pole.

Electric Generators (Dynamos)

Electric generators work by using a coil of wire that can rotate between two permanent magnets.
The movement of the wire causes it to cut through the magnetic field, inducing a potential difference.
If the coil is connected to a complete circuit, an alternating current (AC) will flow.
Direct current (DC) is produced if the ends of the coil are connected to a split ring commutator.

Transformers

Transformers work by using an AC current in the primary coil to create a changing magnetic field.
The changing magnetic field induces a current in the secondary coil.
If the primary current is DC, the magnetic field is constant, and no current is induced in the secondary coil.
Step-up transformers have more coils on the secondary, increasing the voltage, while step-down transformers have fewer coils, decreasing the voltage.

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Description

Test your knowledge on topics related to magnetic fields and currents. Learn about the relationship between current and magnetic fields, the right hand grip rule, strength of magnetic fields, and the magnetic field shape of a solenoid.