BBC Bitesize - KS3 Physics - Electric current and potential difference - Revision 6
Flow of Charge Charge flows from a potential difference (voltage), between the ends of a conductor. current is related to voltage that produces it, and resistance that opposes it. . These are found by simply substituting Ohm's Law equation. 4 Voltage. Definition of the volt. 5 Resistance and Ohm's law. Ohm's Law The SI unit of current is the ampere (symbol A). and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 x newton per meter of length. . determines the relationship between these three units. Unit 7: Electricity and magnetism. Unit 7. Electricity and magnetism. Index. 1. .. The potential difference, also known as voltage, is the energy required to The relationship between Voltage, Current and Resistance in any electrical circuit.
Generators—like alternators in cars or turbines in power plants— convert mechanical energy to electrical energy. PE diff 11 Consider a long pipe filled with water. Water flows through a pipe if there is a difference in pressure across the pipe between its ends. Water flows from high pressure to low pressure. Voltage does NOT flow through a circuit. Voltage Sources 12 The amount of charge current that flows depends on the voltage source, and on… electric resistance: Thick wires have less resistance.
Longer wires have more resistance. Electric Resistance Certain metals acquire superconductivity zero resistance to the flow of charge at temperatures near absolute zero. How do batteries and generators cause current to flow through a wire? Which of the following type of copper wire would you expect to have the least electric resistance? Toasters have a resistance of ohms.
How much current is drawn by a lamp that has a resistance of ohms when a voltage of 50 volts is impressed across it? You would not feel 12 V, and 24 V would just barely tingle.
With moist skin, however, 24 V could be quite uncomfortable. If the resistance of your body wereohms, what would be the current in your body when you touched the terminals of a volt battery? If a current of 0. When you double the voltage in a simple electric circuit, you double the … A.
To receive an electric shock there must be… A. The source of electrons in a circuit is the conducting circuit material itself. The Source of Electrons in a Circuit 31 When plug into an outlet, energy flows from the outlet, not electrons.
GCSE Science/Current, voltage resistance and Ohm's law - Wikibooks, open books for an open world
Energy is carried by the electric field which vibrates electrons already there. Electrical energy is converted to mostly heat and some light. The strength of the electric field electric field strength E is described by considering how much force is experienced by a unit charge a charge of 1 coulomb when it's placed in the field.
The electric field at any point is therefore expressed in newtons per coulomb. Some fields such as the field between two parallel charged plates have the same field strength throughout the field - uniform fields. Others particularly radial fields due to isolated point charges do not have constant field strength.
In a battery there is a negative and positive terminal. The conventional current flows from positive to negative the large line to the small line. Because opposites attract, these charges in the battery will be attracting each other, but they can not move directly to each other through the battery because of the chemical processes. If there is a complete external circuit, this attraction from the battery will give the free electrons in the metal i.
If you think about it these electrons are being forced to the other side of the battery because of this attraction. We call this driving force the Electro-motive Force e.
Emfs are measured in volts, and are sometimes referred to simply as voltage. The larger the emf the voltage the more quickly electrons flow round the circuit.
What is the rate of flow of the electrons? Current[ edit ] Now imagine that you were to put your finger on one pea and push it in a clockwise direction.
BBC Bitesize - GCSE Combined Science - Electric circuits - Edexcel - Revision 3
All the peas would move because they are all touching one another. This is just what happens when an electric current flows. Current is the flow of charged particles the particles are usually electrons. The SI unit of current is the ampere symbol A.
To understand how current is defined think of standing at a given point in the wire. Electrons are flowing past you. One Ampere is a flow of one coulomb going past every second. The ampere is defined in terms of the force produced between two wires each carrying identical currents: Voltage[ edit ] Having looked at charge and current, we now need to look at what voltage means.
As you know, electrons repel each other.
If you hold one electron near another electron, you have to push against it to hold it in place. If you try to bring it even closer, you have to do work force times distance to get it to that new position.
The voltage between one point and another is simply how much work per coulomb is required to move any small test charge from point A to point B. In most electronic components, it doesn't matter much which path the test charge takes in-between point A and point B.
Voltage is related to the energy of the charges. Let's go back to the peas in the petri dish.
They can be pushed slowly or they can be pushed quickly. The faster they go, the more energy they have.Electric Potential, Current, and Resistance
It's a similar situation for the electrons, except the push isn't provided by a finger! It's provided by the battery. The battery gives the charges energy. This energy is given up to the various components in the circuit, e.
GCSE Science/Current, voltage resistance and Ohm's law
The energy per unit charge is called the voltage or the potential difference. Definition of the volt[ edit ] One volt means one joule of energy per coulomb of charge. More accurately it has 2 definitions: Electromotive Force is the amount of energy converted from non-electrical to electrical form when driving 1 coulomb of charge around a completed and closed circuit.
Potential Difference is the amount of energy converted from electrical to non-electrical form when driving 1 coulomb of charge around a completed and closed circuit. The potential difference between 2 points in a conductor is defined as 1 volt, if 1 Joule of energy is converted from electrical form to non-electrical form, when 1 coulomb of charge per second 1 amp flows through it. This will only occur between 2 points in a conductor, that has a resistance, defined as 1 ohm.
It's just how difficult it is for the charges to flow through an electrical component or from one point to another in an electrical circuit. Imagine a group of walkers travelling down a road.