CH 18: Practical Electricity

• Electricity is used in household electrical appliances to convert electrical energy into other useful energy such as light, solar, thermal, and kinetic energy.
• Potential difference is the energy needed to move one unit of charge across two points.
• Current is the rate of charge per unit time.
• Energy equals the product of potential difference and current, represented by the equation E = VI.
• Power is the rate of electrical energy conversion, represented by the formula P = E/T.
• Dissipated power is the power dissipated by passive components or components that consume energy in a circuit, represented by the formula P = i²r or P = v²/r.
• Input power is the power consumed by active components or components that provide energy in a circuit, represented by the formula P = v i.
• The unit for energy is Joules (J), but kilowatt hour (kWh) is more commonly used, especially in calculating electricity cost.
• An air conditioner rated at 1500 watts used for 8 hours a day for 30 days would cost 90 dollars in electricity.
• The formula for calculating the cost of electricity is Energy = Pt, where P is power in kilowatts and t is time in hours.
• A short circuit provides a path with much lower resistance than intended for electric current to flow, hence the current flows out from the positive terminal of the battery and chills the short circuit, avoiding flowing into the lamp and returning to the negative terminal of the battery, causing the light bulb to not shine.
• The live wire ring is set at 240 volt and the neutral wire ring is set at zero volts, and when an appliance is plugged in, it has physical contact between the live and neutral wiring, closing the circuit and producing a potential difference between the two ends of the appliance, allowing current to flow through it.
• Overheating of cables and wires can melt insulators and pose a risk of electric shock.
• Ring design in home electric circuit allows for safe use of electricity.
• Electrolytes in water are an electrical conductor, so if we handle electrical cables, plugs, and appliances with wet hands or in damp conditions, the electric current can travel through the water and cause electric shock.
• The voltage supply to home is set at 240 volt, and the current i is calculated by i equals to 240 over r, where r is a small amount of resistance.
• If cables or wires carry more current than they are designed to carry, they will become very hot, and the rate of heat generated p can be calculated by formula p equals to i square r.
• It is dangerous to install a socket near the ground, especially in toilets, as the condition near the ground is usually wet, which can lead to electric shock.
• In a ring design, the blue wire is the neutral wire and the red wire is the live wire, which are connected to the main circuit breaker, electricity meter, main switch, and 30 amps circuit breaker.
• Overheating of cables and wires due to high current can cause fires.
• A fuse is a safety device that protects a circuit from excessive current flow when the excessive current flows through the fuse it will melt or blow and break the circuit, and the fuse is always connected to the live wire, as excessive current will blow the fuse first before flowing into the appliance connected to the circuit.
• The earth wiring provides a low resistance connection to the ground to prevent users from getting electric shock.
• Short circuits can cause danger as excessive flow of electric current can cause danger.
• Electricity can be saved by using circuit breaker as it trips when it detects a port in the circuit.
• Circuit breakers are usually located in the electric box along with switches and fuses.
• A circuit breaker has similar function as fuels it trips when it detects a port in the circuit.
• A blown field needs to be replaced however a circuit breaker only needs to be reset after it is tricked.
• There are three main types of circuit breakers the first one is miniature circulator or mcb it trips and disconnects the mains electricity supply to a house automatically when it detects excessive current flow by tripping or breaking the circuit.
• The current rating of a fuse is the minimum amount of current that will blow the fuse.
• Common fuels available in the markets are 1 amps, 2m, 5 amps, 10 amps and 13 amps.
• The third circuit breaker is residual current detector rcd it trips and disconnects the mains electricity supply when it detects a difference in the amount of current between live and neutral wires this indicates there is the current leakage.
• A fuse with current rating slightly higher than the normal working current is chosen to be used in a circuit.
• The second type is earth leakage circuit breaker elcb it trips and disconnects main electricity supply when it detects current flowing in the earth circuit when there is current in the earth wire it indicates current leakage from live wires.
• A circuit breaker only needs to be reset after it is tricked.