FORM 5CHAPTER 3

ELECTROMAGNETISM

LEARNING AREA…• 3.1 Analysing the Magnetic Effect of a

Current-carrying Conductor• 3.2 Understanding the Force on a Current-

carrying Conductor in a Magnetic Field• 3.3 Analysing Electromagnatic Induction• 3.4 Analysing Transformers• 3.5 Understanding the Generation and

Transmission of Electricity

3.1 Analysing the Magnetic Effect of a Current-carrying

Conductor• Learning Outcomes…

– state what an electromagnet is.– draw the magnetic field pattern due to

a current in a:i. straight wire, ii. coil, iii. solenoid.

– plan and conduct experiments to study factors that affect the strength of the magnetic field of an electromagnet.

– describe applications of electromagnets.

Electromagnetism…

• Is a magnet made by winding coil of insulated wire around a soft iron core, so that a magnetic field is produced when a current is passed through the coil.

• Can be formed by winding about 20 turns of insulated copper wire round a soft-Iron core such as a soft-iron nail.

• Its magnetism is temporary and can be switched on and off.

Electromagnetism…

Electromagnetism…

• Straight Wire

Magnetic Field Pattern & Direction of the Magnetic Field

Due to a Current…• Straight Wire• Straight Wire• Determines by

– Magnetic Field in a Straight Wire– Magnetic Field in a Coil– Magnetic Field in a Solenoid

• Straight Wire

Magnetic Field Pattern…

• Straight Wire• Straight Wire• Straight Wire– Two methods to determine

direction of the magnetic the field:•Right-hand grip rule•Maxwell’s screw rule

• Straight Wire

Magnetic Field Pattern… Straight Wire

• Straight Wire• Right-hand grip rule

The thumb aligns with the current flows while the fingers determine the magnetic field direction.

• Straight Wire• Straight Wire• Straight Wire• Maxwell’s screw rule

The direction of rotation of the screw gives the direction of the magnetic field if the screw move forward in the direction of the current in the wire.

Magnetic Field Pattern… Straight Wire

Magnetic Field Pattern… Straight Wire

Magnetic Field Pattern… Straight Wire

Current out - anticlockwise Current in - clockwise

Magnetic Field Pattern…Circular coil

Magnetic Field Pattern…Circular coil

Magnetic Field Pattern…

Solenoid

Magnetic Field Pattern…

Solenoid

Magnetic Field Pattern…

Solenoid

Methods to determine the poles of a solenoid:

Magnetic Field Pattern…

Solenoid

Methods to determine the poles of a solenoid:

Factors Affecting the Strength of the Magnetic Field of an Electromagnet

Factors Affecting the Strength of the Magnetic Field of an Electromagnet

Factors Affecting the Strength of the Magnetic Field of an Electromagnet

Factors Affecting the Strength of the Magnetic Field of an Electromagnet

Factors Affecting the Strength of the Magnetic Field of an Electromagnet

Application of Electromagnet

Application of Electromagnet

• Time to answer the questions……– Mastery Practice 3.1– Challenge Yourself

• Page 78 & 79