Ký Tự Đặc Biệt Trong Nội Dung

Effects of Electric Current

• Various electrical devices in a home use electric current, transforming it into different forms of energy.
• Examples of electrical devices include electric bulbs, electric fans, induction cookers, and storage batteries (while charging).
• Electrical energy is converted into different forms of energy within these devices.
• The different forms include heat energy, which is notable in heating devices like appliances or electric irons.

Table 1.1

• Shows how devices transform electrical energy into other forms.
• Electrical energy is transformed into heat energy in devices like light bulbs or electric stove(s).

Heating Effect of Electric Current

• Electric irons are examples of devices that harness the heating effect of electric current.
• Electrical energy changes into heat energy within these devices.
• Experiments use a nichrome wire, a 6 V battery, and connecting wires.

Joule's Law

• Heat generated (H) in a current-carrying conductor is directly proportional to the square of the current (I²), the resistance of the conductor (R), and the time (t) of current flow.
• The formula for heat generated: H = I²Rt
• I represents current in amperes (A)
• R represents resistance in ohms (Ω)
• t represents time in seconds (s)

Complete Table 1.2

• Shows calculations for a conductor with different resistance values if it is known.

Parallel Connection

• Resistors' combined resistance decreases when connected in parallel, since the current is split across individual branches.
• The formula for combined resistance is: 1/R = 1/R₁ + 1/R₂ + 1/R₃...

Resistors in Series

• When resistors are connected end-to-end (in series), the combined resistance of the circuit increases.
• The formula for combined resistance in a series circuit is: R = R₁ + R₂ + R₃...
• The current through each resistor in a series circuit is the same.

Colour Codes for Resistors

• Understanding color codes on resistors is important for determining their resistances.
• Resistors usually have four color bands.
• Color codes are used (e.g. Black is 0, Brown is 1) to determine the value of the resistors.

Joule's Law Practical

• Experiments can illustrate how the current, resistance, and time affect the amount of heat developed when electrical current flows through an electrical conductor.
• Use beakers with different resistance wires (wires such as copper and nichrome).
• Observe how the heat generated differs based on the resistance.

Appliances Without Heating Coils

• Devices such as microwave ovens and induction cookers use methods other than heating coils to perform their functions.

Safety Fuse

• Fuse wires protect circuits from excessive currents.
• They melt (and break the circuit) when a higher current than designated for that circuit is applied, preventing potential damage to the circuit.

Electric Power

• Power is the rate at which electrical energy is converted to another form.
• Power (P) is calculated using the formula: P = W/t = VI = I²R = V²/R
• Units: watts (W)

Lighting Effect of Electric Current

• Filament lamps use tungsten filaments, producing light when heated by electricity.

Discharge Lamps

• Fluorescent lamps and LED lamps are examples of discharge lamps that work differently from filament lamps.

LED Bulbs

• LED bulbs use semiconductor diodes to emit light using low power.
• LED bulbs have a longer lifespan and are more efficient compared to incandescent lamps.

Tools for Repairing LED Bulbs

• Specific tools, such as soldering irons, multimeters, and pliers, are used to repair damaged LED bulbs.

Assessment

• Problems and examples are given for evaluating the understanding of electric current's effects
• Includes practical calculations of current or power, using formulas and given data.