A battery is defined as an electric power source, made up of one or more electrochemical cells, for powering external electric connections to devices like flashlights, electric cars and mobile phones. A battery has a positive terminal, called the cathode, and a negative terminal called the anode.
Many of us use the terms battery and cell interchangeably but they are a little bit different. A battery normally contains electrical energy supplied from a company and is easily rechargeable from an external source. A cell is made up of chemical sources of energy such as natural gas, diesel, or propane. A cell converts these sources to electrical energy and generates power.
Electrical energy is often used in various applications such as in operating devices like radios, computers, televisions, telephones, and high-speed trains. Electrical energy is also used in the production of light and heat. The transfer of energy is a result of the flow of electrons. The electric circuit is the name given to the complete path along which the charges flow. Let’s dig in and find out more.
LEARNING OBJECTIVES
By the end of this topic, you are expected to;
SIMPLE CIRCUITS
A circuit is a closed loop that electrons can travel in. Unless a circuit is complete (makes a full circle), electrons cannot move, thus the name circuit.
An electric circuit is a path through which electric current is transmitted. It consists of: a device giving energy like a cell, generator or battery, devices using current like torch or bulb, and connecting wires.
To set up a simple circuit, you need a light bulb, connecting wires, a battery, and a switch.
When the switch is closed, the bulb lights but when the switch is open the bulb does not light. The bulb lights when the circuit is closed because charges are flowing through it. The rate of flow of charges (per unit time) is referred to as an electric current. Ampere (A) is the SI unit of current.
I = Q ∕ t where I represent current, Q represents charge in coulombs and t represents time in seconds.
For example,
Calculate the amount of current that flows through a bulb when 300 coulombs of charge flows through it for 2.5 minutes.
Solution
Here we convert 2.5 minutes into seconds by multiplying it by 60 (as 1 minute = 60 seconds).
I = Q ∕ t = 300 ∕ (2.5 x 60) = 2 A
An electric current circuit allows the movement of charges in a complete path when the switch is closed. This is called a closed circuit. Copper wire readily allows charges of electricity to flow. The wires can be covered by an insulating material such as rubber for the prevention of the user from electric shock. The source of electrical energy in the circuit is the cell and it maintains the flow of charges around the circuit.
When the switch is opened by introducing the gap, charges stop flowing. Then, the circuit is said to be open. Loose connection of components or wires opens or breaks the circuit.
ELECTRICAL SYMBOLS USED IN DRAWING CIRCUITS
ELECTROMOTIVE FORCE AND POTENTIAL DIFFERENCE
The purpose of a battery or cell in a circuit is the provision of energy to make charges flow. This is measured in terms of potential difference (p.d) in volts. Voltage is the force that pushes electrons around the circuit.
Potential difference. This refers to the voltage measured across a battery or cell when supplying current.
Electromotive force. This is measured across a cell or battery when it is not supplying current. It is also measured in volts.
Electromotive force is often greater than the potential difference since some of the energy is used in passing current across the cell itself. Lost volts is the name given to the difference between potential difference and electromotive force. The voltage is lost as a result of opposition to the flow of charges in the cell (internal resistance).
ARRANGEMENT OF CELLS
Cells can be arranged in series or in parallel. A series arrangement is when cells are connected in a manner that the positive terminal of one is joined to the negative terminal of another one. Two or more cells connected in series make a battery.
The parallel arrangement is when cells are placed side by side. The positive terminals are connected together and the negative terminals the same.
CONDUCTORS AND INSULATORS
Conductors are materials that can conduct electricity. They permit electric current to pass through them. They include copper, aluminum, and silver.
Insulators are materials that do not allow electric charges to pass through them such as plastics, dry wood, and rubber.
