Flashcards
Electric current P2T2
Cards in this deck (16)
- 1What is current?Current is the rate of flow of charge around a circuit. It is carried by electrons; metals are good conductors because they have free electrons which are free to move around. Measuring the amount of current flowing past a point during a length of time measures how much charge has passed.
- 2What is voltage (potential difference) and what is it measured in?Voltage is the electrical pressure that causes a current to flow in the circuit. It is measured in volts. A volt is the amount of energy given by power source to each coulomb of charge in a circuit.
- 3What is resistance?Resistance in a circuit is provided by a resistor, it slows down the current by absorbing power. Variable resistors can control how much current flows through a component.
- 4What is the relationship between voltage and resistance?Voltage is the driving force of the current, however, resistance opposes this. Their sizes decide how big the current will be. Increasing the voltage means more current will flow. Increasing the resistance means less current will flow.
- 5How is energy transferred?Energy is transferred when an electrical charge goes through a change. For example, energy is provided to the charge by a power source, however, a resistor in the circuit will oppose the voltage, decreasing the energy the charge has. This change in voltage means that energy is transferred.
- 6What is the junction rule?In a parallel circuit, the current from the power supply is split along the junction. The amount of current flowing when it rejoins at the other junction will be the same at it was when it split.
- 7What are the functions of the components in a circuit and where are they placed?A standard circuit consists of an ammeter, which measures the current flowing through a component, therefore, it must be placed in series. A voltmeter measures the voltage across the component, which means that it must be placed parallel to the component.
- 8Explain a fixed resistor graph. (V=IR)In a fixed resistor graph the current and voltage are directly proportional. This is because as the voltage increases, the resistance stays the same, so there is nothing to slow down the current.
- 9Explain a filament lamp graph. (V=IR)A filament lamp contains a thin coil which, as electric current passes through it, heats up so much that it produces light. As the temperature of the filament increases, the resistance increases too. This is because too much energy could make the bulb burn out so the resistor absorbs it. That's why the current and voltage are not directly proportional.
- 10Explain a diode graph. (V=IR)A diode has a very high resistance in one way which means that the current can only flow in the other direction. In this graph, the resistance it so much that even increasing the voltage doesn't make the current flow. However, as the resistance is decreased the current suddenly increases very rapidly.
- 11What is an LDR (light-dependent resistor)?LDR is a type of resistor that changes its resistance according to how much light there is. If it is bright, then the resistance decreases. If it is dark, then the resistance increases.
- 12What is a thermistor (temperature-dependent resistor)?This is a type of resistor that changes its resistance according to the temperature. In hot conditions, the resistance decreases. In cold conditions, the resistance increases.
- 13What causes a heating effect in a circuit?Resistors get hot when an electric current passes through them as energy is transferred. This happens because of the electrons colliding with the ions in the lattice which make up the resistor. These collisions give the lattice extra energy which is emitted as heat. This increases the resistor's resistance which means that less current will flow. If it gets too hot, the current will stop flowing completely.
- 14What are the advantages of the heating effect?The heating effect can be useful is heating things with the wasted energy, For example, toasters have a coil of wire inside them with a very high resistance. As electric current flows through it, the wire 's temperature rises so much that it glows and gives off heat which cooks the bread.
- 15What are the disadvantages of the heating effect?Resistors emitting too much heat can make the appliance less efficient, as some energy is wasted as heat. It can also cause components to melt and stop working. Fuses use this process to protect a circuit, they have current higher than the circuit and contain a wire which melts if the current gets too high.
- 16What is electrical power?The electrical power of an appliance is the rate of energy transferred for an amount of time. This depends on how much current is flowing through the component. So an appliance with a high power rating will draw more current from the supply.
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- GCSE Additional Science Flashcards on Electric current P2T2, created by Aleesha Ali on 16/04/2016.
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