Magnetic Field and Current Quiz

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.