Circuits Flashcards
What is a thermistor, explain 3 facts…
A thermistor is a temperature dependant resistor. Thermistors make useful temperature detectors, e.g. Car engine temperature sensors and electronic thermostats in hot conditions, the resistance drops, in cool conditions the resistance goes up.
What is a light emitting diode, explain 3 points…
A light-emitting diode (LED) emits light when a current flows through it in the forward direction. LEDs indicate the presence of current in a circuit. Often used in appliances (e.g. TVs) to show that they are switched on. They are also used for the numbers on digital clocks, in traffic lights, and in remote controls. They are also used in lighting because they use a much smaller current than other forms of lighting.
What is a light dependant resistor, explain 3 points…
An LDR is a resistor that is dependant on the intensity of light. They have lots of applications including automatic night lights, outdoor lighting and burglar detectors. In bright light the resistance falls, in darkness, the resistance is highest.
What does resistance mean?
The degree to which a component impedes (prevent/obstruction of something) the passage of current. Shown by the letter R. The unit of resistance is the ohm.
Explain 3 points about a diode…
A diode is a special device made from semiconductor material such as silicon. Diodes are used to regulate the potential difference in circuits. It lets current flow freely through it in one direction, but not in the other(i.e. there is a very high resistance in the reverse direction). This is useful in various electronic circuits.
Explain the different resistors on potential difference-current graphs…
The current through a resistor (at a constant temperature) is directly proportional to P.D. Different resistors have different resistances, hence the different slopes.
Explain the different resistors on potential difference-current graphs…
As the temperature of the filament increases, the resistance increases, hence the curve.
Explain the diode on potential difference-current graphs…
Current will only flow through a diode in one direction. The diode has very high resistance in the opposite direction.
Resistance, potential difference and current, what is the word and symbol equation?
Potential Difference = Current x Resistance
V = I x R
What are the 2 main types of parallel circuits?
Independence and Isolation
Independence and Isolation, explain 2 points…
In parallel circuits, each component is separately connected to the +ve and the -ve of the supply. If you remove or disconnect one of them it will hardly affect the others at all. This is how most things must be connected, for example in cars and in household electrics. You have to be able to switch everything on and off separately.
P.D. Is the same across all components, state why?
- In parallel circuits all components get the full source P.D., so the voltage is the same across all the components:
V1 = V2 = V3 - This means that identical bulbs connected in parallel will all be at the same brightness.
Current is shared between branches, state why?
- In parallel circuits the total current flowing around the circuit is equal to the total of all the currents through the separate components. A = A1 + A2 + …
Current is shared between branches, state why?
- In a parallel circuit, there are junctions where the current either splits or rejoins. The total current going into a junction has to equal the total current leaving.
Current is shared between branches, state why?
- If two identical components are connected in parallel then the same current will flow through each component.
