Topic: Electric Energy

WEEK: 9 & 10

## Introduction

The matter is made up of atoms. Each atom has protons, neutrons and electrons. The protons and neutrons are at the centre of the atom (that is, the electrons orbit the nucleus of the atom, which is the source of the atom’s electrical energy, while protons and neutrons are located in the centre of the atom.

## Meaning Of Electrical Energy

Electrical energy  Energy is the capability to do work. Heat, kinetic or mechanical energy, light, potential energy, and electrical energy are all different types of energy that can be found in the universe. Energy Measured in Units: The joule (J) or the newton-meter (N * m) is the unit of energy that is used in the SI system. Work is measured in joules, which are also the SI unit of measure for energy. This energy is created when electrons move or flow freely through a conductor. Long cables, which are referred to as Main Lines, are used to carry the signal from one location to another.

## Flow Of Electrons

Some materials allow the flow of electrons while others do not. Materials that allow the flow of electrons in them are called conductors while materials that do not allow the flow of electrons in them are called insulators. Examples of conductors are silver and copper while examples of insulators are glass and mica.

Some types of matter make it possible for electrons to flow through them, albeit with significant resistance. These materials, called resistors, make it hard for electrons to move through them. For example, iron is more difficult for electrons to move through than copper. So, copper conducts electricity better than iron. The flow of electricity is controlled by resistors.

There are two types of electron flow, which include:

1. Direct current
2. Alternating current
• Direct current (DC): This is an electric current in which electrons flow in only one direction. DC is a flow of electrons from negative to positive all the time. This kind of electron flow can be seen in batteries, solar cells, and other places. It is used in many applications with low voltage.
• Alternating current (AC): This is a type of electric current in which electrons move in two directions, from the positive terminal to the negative terminal and back again.

## Series And Parallel Circuits

An electric circuit is the arrangement of sources of electric current and conductors through which a current can flow continuously. A small light bulb, a battery, and two pieces of wire can be used to set up a simple circuit. Electricity will flow from the negative end of the battery through one of the wires, through the wire inside the light bulb, through the other wire, and back to the positive end of the battery. When electricity flows through the filament and heats it up, the bulb turns on. Circuits can be set up in either a series or a parallel pattern.

### Series circuit

Connecting the right end of one resistor to the left end of another resistor puts them in a series. Electric current flows through resistors connected in series against the resistance of each resistor. As a result, the total resistance to current flow equals the sum of the individual resistances.

When three resistors with resistances R, Rj, and R3 are connected in series, the total resistance are;

Rtotal = R1+R2+ …Rn

Vtotal = V1=V2=…Vn

Here, we have three resistors (R1, R2, and R3) connected in a long chain from one terminal of the battery to the other.

The current can only flow in one direction. The current in this circuit flows clockwise from point 1 to point 2 to point 3 to point 4 and back to point 1.

Parallel circuit

The left end of one resistor is connected to the left end of another resistor to form a parallel connection. The resistors are said to be set up in a tree-like structure, with branches leading off to different destinations along the path the current takes from the power supply. When multiple resistors are wired in parallel, the combined resistance is lower than that of any one of the resistors used alone. This is because electric current can take multiple routes (branches) in a parallel circuit, but there is only one route (path) in a series circuit.

A resistor parallel connection’s total resistance is given by:

Rtotal = 1/R1+1/R2+ …+1/Rn

Vtotal = V1=V2=…=Vn

Itotal   =I1+I2+…In

## Functions Of Some Circuits Of Household Materials

#### Ammeter and voltmeter

An ammeter is a device that measures the quantity of electric current flowing through a given circuit. An ammeter is connected in series to get an accurate reading of electric current in a circuit. This is essential due to the fact that all components of a series circuit must share the same current. Ampere (A) is the unit of measurement for electric current.

A voltmeter is a device that measures the amount of electric potential (voltage) in a circuit. The parallel connection of a voltmeter ensures accurate readings (V). #### Fuse and circuit breaker

Circuit breakers and fuses are both types of devices that are made to immediately cut off power from the mains if the current goes over the fuse rating. fuses The use of fuses and circuit breakers in household wiring is very important.

Fuse

A fuse is an electrical safety device that has a piece of metal that melts if the current running through it goes over a certain level, breaking the circuit. A fuse is made of alloys of tin and leads with low melting points.

Circuit breaker

A circuit breaker is another electrical safety device. It doesn’t melt, but it trips to stop the flow of electricity.

#### Electric meter reading and billing

An electric meter is a tool for measuring electrical resistance and current usage. An electric meter is used to determine the amount of power consumed by an electrical appliance or resistance. There are two kinds of electric meters:

• Prepaid meter
• Postpaid meter

Electric utilities in Nigeria, such as Ikeja Electricity, have installed electric meters at consumers’ homes for billing purposes. They are usually calibrated in billing units, the kilowatt-hour (kWh) being the most common. Watt-hour (kWh) is a convenient unit for measuring cumulative energy consumption. To calculate the electricity bill of a consumer, the following must be considered;

1. The total power rating of appliances in kilowatts.
2. A number of hours appliances are on.
3. Amount in kilowatts.
4. The number of units in kilowatts per hour is power (kW) x time (hour (h))
5. Charge per unit.
6. Meter Maintenance Charge (MMC)

### Example 1

assum[ing] that the price of one kilowatt-hour of energy (or 1 kWh) is 5 kobo. In a house, you’ll most likely find:

• Fifteen 50W electric bulbs.
• One electric kettle of 500 watts.

a) Assuming the electric bulbs are used for 5 hours per day for 30 days. Find the quantity of energy consumed by electric bulbs and the cost

b). The electric kettle is used for six minutes per day for 30 days. What is the quantity of energy consumed by the electric kettle and its cost?

Solution

1. a) quantity of energy consumed

Energy =Power (kW) x Time (h)

Power consumed by the 15 bulb=

50W x 15 = 750W = 0.75kW

Time = 5hrs

Energy 0.75kW x 5h

Energy consumed by the 15 50W bulb for 30 days = 3.75kWh x 30.

Total energy = 112.5kWh

The cost = Energy x cost per kWh = 112.5kWh x 5kobo

= 562.5kobo

= 5.63 Naira

1. b) The quantity of energy consumed by the electric kettle is given by:

Power = 500W = 0.5kW

Time = 6min = 0.1h

Cost per kWh = 5kobo

The total energy consumed for 30 days

= 0.5kW x 0.1hr x 30days

= 1.5kWh

The cost of the energy consumed

=1.5 x 5kobo = 1.5kWh x 0.05 naira

=7.5kobo

### Example 2

If power = 10KW

Time = 10 hrs

Unit charge  = N5.00

MMC = N150.00

Calculate the bill for the month

Solution:

Number of units in kWh = Power x Time

= 10 x 10

= 100kWh

The electricity bill for the month = Number of units in kWh x Unit charge + MMC

= (100 x 5) + 150

= 500 + 150

= N650