Question

GRADE: 9
PERIOD: V
TOPICS: MAGNETISM AND ELECTRICITY
Magnetism:
a) Causes
b) Properties
c) Magnetic field
d) Magnetic field
production
2. Types of magnets:
a) Horse-shoe
b) Bar
c) Electro-magnets
d) The Graham bell
3. Compass: - Uses
4. Motor and Dynamo:
5. Effect of lightning and
thunder on electrical
appliances
6. Electric Current:
a) Types
) Effects on metals
and non-metals
7. Measurement of
electric current
8. Ohm’s Law
9. The S.I. Units
10.Types of transformers:
a) Step-up
b) Step-down
11.Circuits:
a) Series
b) Parallel
12.Circuit breakers and
fuses
Electrolysis

Answer 1

## Grade 9: Magnetism and Electricity

### 1. Magnetism
a) **Causes**:
- Magnetism is caused by the motion of electrons within atoms. When electrons move, they create magnetic fields.
- Permanent magnets have regions where the magnetic fields of many atoms align in the same direction.

b) **Properties**:
- Magnets attract materials like iron, nickel, and cobalt.
- A magnet has two poles: North and South. Like poles repel each other while unlike poles attract.
- Magnetic fields can penetrate non-magnetic materials, but their strength decreases with distance.

c) **Magnetic Field**:
- A magnetic field is a region around a magnet where magnetic forces can be detected.
- The strength and direction of a magnetic field can be represented using magnetic field lines.

d) **Magnetic Field Production**:
- Electric currents produce magnetic fields (Ampère's circuital law).
- Coiling a wire increases the strength of the magnetic field produced by an electric current.

### 2. Types of Magnets
a) **Horse-shoe Magnet**:
- A U-shaped magnet that provides a strong magnetic field and is useful for lifting magnetic materials.

b) **Bar Magnet**:
- A rectangular magnet that exhibits a uniform magnetic field and can be used in various applications, including compasses.

c) **Electro-magnet**:
- A magnet that is created by passing an electric current through a coil of wire, often wrapped around a ferromagnetic core; strength can be controlled.

d) **The Graham Bell**:
- This likely refers to inventions by Alexander Graham Bell related to magnetic telephony, highlighting the role of magnetism and electricity in communication.

### 3. Compass: Uses
- A compass is an instrument that uses a magnetized needle to indicate the direction of Earth's magnetic north.
- Commonly used for navigation, in hiking, or determining directions in geography.

### 4. Motor and Dynamo
- **Motor**: Converts electrical energy into mechanical energy using the interaction between a magnetic field and electric current.
- **Dynamo**: Converts mechanical energy into electrical energy through electromagnetic induction.

### 5. Effect of Lightning and Thunder on Electrical Appliances
- Lightning can induce voltage surges in electrical systems, which may damage electrical appliances.
- It is important to use surge protectors to mitigate damage from lightning strikes.

### 6. Electric Current
a) **Types**:
- **Direct Current (DC)**: Flows in one direction; used in batteries.
- **Alternating Current (AC)**: Changes direction periodically; used in homes and industries.

b) **Effects on Metals and Non-metals**:
- Metals, being good conductors, allow electric current to flow easily and can heat up or magnetize.
- Non-metals are generally poor conductors and may not allow current to flow.

### 7. Measurement of Electric Current
- Electric current is measured in amperes (A) using an ammeter.

### 8. Ohm’s Law
- Ohm’s Law states that the current (I) through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) of the conductor:
\[ I = \frac{V}{R} \]

### 9. The S.I. Units
- **Electric Current**: Ampere (A)
- **Voltage**: Volt (V)
- **Resistance**: Ohm (Ω)
- **Power**: Watt (W)

### 10. Types of Transformers
a) **Step-up Transformer**:
- Increases voltage from primary to secondary coil, decreasing current; used in power transmission for high voltages.

b) **Step-down Transformer**:
- Decreases voltage from primary to secondary coil, increasing current; used for supplying household voltage.

### 11. Circuits
a) **Series Circuit**:
- Components connected in a single path. If one component fails, the entire circuit stops functioning.

b) **Parallel Circuit**:
- Components connected in multiple paths. If one component fails, others continue to operate.

### 12. Circuit Breakers and Fuses
- **Circuit Breakers**: Automatically interrupt the flow of current in the event of an overload. They can be reset.
- **Fuses**: A safety device that melts and breaks the circuit if the current is too high, preventing damage.

### Electrolysis
- A process that uses electrical energy to cause a chemical change, usually to separate elements from their compounds. Commonly used in electroplating and purifying metals.

This guide summarizes key concepts in magnetism and electricity for Grade 9, providing a comprehensive understanding of the topics to assist in studies.