Physics 2024-07-16 Key Terms Conductors Conductors are materials that allow the flow of electric current through them due to the presence of free electrons. Conductors have high electrical conductivity, allowing electric charges to move easily. Metals are excellent conductors due to the large number of free electrons. Conductors can be used to transfer electrical energy efficiently. The conductivity of a conductor depends on its resistance and the temperature. Current Current is the flow of electric charge through a conductor. Current is measured in amperes (A). Current can be either direct (DC) or alternating (AC). The direction of current is the direction of positive charge flow. The rate of flow of current is determined by the voltage applied and the resistance of the conductor. Electrical energy Electrical energy is the energy carried by electric currents, which can be used to power electronic devices and produce light, heat, and motion. Electrical energy is generated by the movement of charged particles, such as electrons. Electricity can be converted into other forms of energy, such as mechanical energy or thermal energy. The unit of electrical energy is the watt-hour (Wh) or kilowatt-hour (kWh). Electrical energy can be stored in batteries for later use. Electrical power Electrical power is the rate at which electric energy is transferred or converted to other forms of energy. The unit of electrical power is called the watt, symbolized by the letter 'W'. The formula to calculate electrical power is P = IV, where P is power, I is current, and V is voltage. Electrical power can be transferred through various devices such as wires, resistors, and transformers. Evaluating the power consumption of electrical appliances can help in managing energy usage and reducing costs. Electric Charge Electric charge is a fundamental property of matter that determines whether it is positively or negatively charged. Charge can be transferred from one object to another through physical contact or by induction. Opposite charges attract each other, while like charges repel. The unit of electric charge is the coulomb (C). The absence or surplus of electrons in an object determines its charge. Electric field Electric field is a physical quantity that describes the force experienced by a charged particle in the presence of other charged particles or electrically charged objects. Electric field is a vector quantity, meaning it has both magnitude and direction. The direction of the electric field is defined as the direction a positive test charge would move. Electric field lines represent the direction and strength of the electric field. The magnitude of the electric field decreases with increasing distance from the source charge. Electromotive force Electromotive force, also known as emf, is the electrical potential difference developed by a source of electrical energy that drives charged particles in a circuit. Emf is measured in volts (V) and represents the work done per unit charge in moving a charge from one point to another in a circuit. Emf is provided by sources such as batteries or generators and can be used to power electrical devices. Emf is different from voltage in that it represents the total energy supplied by the source, while voltage represents the energy per unit charge. The direction of the emf is always from the higher potential to the lower potential in a circuit. Insulators Insulators are materials that do not allow the flow of electric current easily due to their tightly bound electrons. Insulators have high resistivity, making them good for preventing the loss of energy through unwanted conduction. Common examples of insulators include rubber, plastic, glass, and ceramic. Insulators are used in electrical wiring and circuit boards to prevent short circuits and ensure safe transmission of energy. Electric charge is generally retained on the surface of insulators instead of flowing through them. Ohm's Law Ohm's Law states that the current passing through a conductor is directly proportional to the voltage applied across the conductor and inversely proportional to the resistance of the conductor. V = I * R, where V is voltage, I is current, and R is resistance. Ohm's Law is named after the German physicist Georg Simon Ohm. It is applicable to both DC (direct current) and AC (alternating current) circuits. Ohm's Law can be used to calculate unknown values of voltage, current, or resistance. Resistance Resistance is a measure of how much a material or device resists the flow of electric current. Resistance is measured in ohms (Ω), and is calculated by dividing voltage by current. Resistors are components specifically designed to introduce resistance into an electric circuit. The longer and thinner a wire is, the higher its resistance will be. Temperature can also affect the resistance of a material, with most materials having an increased resistance as temperature increases.
