| When does a conductor obey Ohm's law | if the current in it is directly proportional to the potential difference across its ends |
| When a conductor does not obey Ohm's law it is decribed as.... | non-ohmic |
| What are Thermistors? | Components designed to have a resistance that changes rapidly with temperature |
| Thermistors are made from? | Metal oxides such as those of manganese and nickle |
| What are the 2 different types of resistors and how does it work (4) | Negative temperature coefficient (NTC thermistors) - resistance of this type of thermistor decreases with increasing temperature
Positive temperature coefficient (PTC) thermistors-the resistance of this type of thermistor rises abruptly at a definite temperature, usually around 100-150 ℃ |
| What is a diode? | any component that allows electric current in only one direction |
| What are modern diodes made from and how do they work | Modern diodes are made from silicon and will start conducting when there is a potential difference of about 0.6V across them |
| What does the resistance of a diode depend on? | on the potential difference across it |
| How does a light-dependent resistor work | If light falling on the LDR is of a high enogh frequency, photons are absorbed by the semiconductor. As some photons are absorbed, electrons are released form atoms in the semiconductor. The resulting free electrons conduct electricity and the resistance of the semiconductor is reduced |
| What are the 2 factors that affect the resistance of a metal: | 1. Temperature
2. The presence of impurities |
| For a metal in the shape of a wire, R depends on the following factors (4) | 1. Length L
2. Cross section area A
3. The material the wire is made from
4. Temperature of a wire |
| What is the formula we use to calculate resistance | (resistivity ✖️ length ) ➗ cross-sectional area |
| What is the formula we use to calculate resistivity | (resistance ✖️ cross-sectional area) ➗ Length |
