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What is an electric circuit?
A closed path along which electrons that are powered by an energy source can flow. The circuit needs a source of electrical energy, usually a cell or battery.
What is a voltaic cell?
A source of energy that generates an electric current by chemical reactions that involve two different metals or metal compounds separated by a solutions that is a conductor. It is also just called a cell. e.g. an AA or D "battery" (cell).
What is a battery?
A connection of two or more cells. e.g. when you place two or more cells in a flashlight, it is a battery.
What is an electrode?
One of two metal terminals in a cell or battery. Both electrodes have to be made of different metals and have to have different abilities to hold onto electrons.
What is electrolyte?
A solution or paste that conducts charge. Electrodes are immersed in electrolyte. Chemical reactions occur at the surface of each electrode that is in contact with the electrolyte.
What 6 types of cells are there?
- Dry cell - A cell that contains an electrolyte that is a paste. Most cells you use are dry cells. e.g. the alkaline cell, zinc-carbon cell, silver-oxide cell and zinc-air cell
- Wet cell - A cell that contains a liquid electrolyte. Most wet cells have a solution of sulfuric acid as electrolyte. e.g. Volta's pile, which had an electrolyte of salt solution.
- Primary cell - A cell that can be only used once. It is then discarded when the electrolyte in the cell runs out e.g. alkaline cell, silver-oxide cell
- Secondary cell - A cell that can be recharged many times. An electric current is passed in the opposite direction through the cell from another source. The charging reverses the chemical reactions in the cell, therefore restoring the cell to full capacity. e.g. lithuim-ion cell, lead acid cell
- Fuel cell - A cell that generates electricity through the chemical reactions of fuel that is stored outside the cell. The by-products are only heat and water. e.g. a hydrogen fuel cell combines hydrogen that's stored in a tank or cartridge with oxygen from the air. This is very environmentally friendly.
- Solar cell - a cell that converts sunlight into electrical energy. e.g. solar panels. When sunlight strikes a semiconductor, electrons are knocked loose from the atoms.
What is a terminal?
A location on a cell that must be connected to other components to form a circuit. There are two terminals, or poles, the positive and negative terminal/pole.
What is a switch?
A control device that can complete or break the circuit to which it is connected. It isn't essential for a circuit to operate and is usually included for convenience.
What is an open circuit?
A circuit that contains a gap or break. Electrons are unable to flow when the circuit is opened, because it creates a gap, so any devices connected to the switch will stop working.
What is electric current?
The rate of movement of electric charge. The current in an electric circuit is due to the flow of electrons.
What are the 2 units to measure potential difference?
- Coulomb(C) - The quantity of charge that is equal to the charge of 6.25 multiplied by 10 to the 18th electrons. This is the unit of electric charge.
- Ampere(A) - The unit of electric current, equivalent to one coulomb per second. For example, 1.0 A in a circuit means that 1.0 C of charge passes at a point every second. Current (amps) is measured using an ammeter.
What is electrical resistance?
The property of a substance that hinders electric current and converts electrical energy to other forms of energy. Free electrons do not get very far until they collide with other electrons in the solid. The collisions interfere with the flow of electrons.
What is a resistor?
A device used in an electric circuit to decrease the current through a component by a specific amount.
What is a load?
A resistor or any other device that transforms electrical energy into heat, motion, sound or light. When electrons collide with metal ions, some of the energy is converted into heat.
What is potential difference (voltage)?
The difference between the electric potential energy per unit of charge at two points in a circuit. It is the difference in electrical potential energy per unit if charge between two points. The unit for potential difference is J(joules)/C(coulomb).
What is a volt?
The unit for potential difference, equivalent to one joule (J) per coulomb (C). A voltmeter is used to measure the potential difference (Volts).
What is a circuit diagram?
A diagram that uses standard symbols to represent the components in an electric circuit and their connections. This is a practical way to describe a circuit.
What are 2 types of circuits?
- Series circuit - A circuit in which there is only one path along electrons can flow. In a series circuit, the specific places where components are connected to the conducting wires are called series connections.
- Parallel circuit - A circuit in which there is more than one path along which electrons can flow. Parallel connections are the specific places where there are more than one pathway.
- Most circuits are a combination of the two.
What is Ohm's law and what is ohm(Ω)?
Ohm's law is the ratio of potential difference to current is a constant called resistance, which is also known as V=IR. The larger the resistance in a particular circuit, the smaller the current is. The unit for resistance is Ω, or ohm, which is equivalent to one volt per ampere (V/A).
What is a superconductor?
A material through which electrical charge can flow with no resistance. A superconducting wire doesn't transform electrical energy into heat. Powerful magnets are usually made using superconducting wires.
What does it mean when a material is non-ohmic?
A non-ohmic material does not follow Ohm's law. e.g. the filament of an incandescent light bulb is non-ohmic, because its resistance increases with temperature. More electrical energy is converted into light energy and the bulb glows brighter when the resistance of the filament is greater.
What are 2 ways loads can be in a circuit?
- Loads in Series - Loads in a series circuit. Adding loads to the series is like increasing the length of the wire. The longer wire would have the greater resistance.
- Loads in Parallel - In a parallel circuit, there is more than one path in which electrons can flow. The total resistance of two loads connected in parallel is less than the resistance of either load.