p4 electrical circuits

• current is the rate of flow of charge
• resistance tries to stop the current from flowing
• resistance is when free electrons collide with fixed vibrating positive metal ions
• as the temperature increases the positive metal ions vibrate faster increasing the resistance
• the length of a wire increasing increases the resistance because there are more positive vibrating ions to get through
• greater diameter of the wire decreases the resistance because there are more gaps to get through
• conductivity of the wire effects resistance
• an ohmic conductor is a conductor that obeys ohms law
• ohms law states that. R=V/I
• when a wire is at a constant temperature it obeys ohms law and is an ohmic conductor so it's graph is a straight line going through the origin (directly proportional)
• a filament lamp doesn't obey ohms law so the graph is a curve because the wire gets hotter and the resistance increases
• a diode doesn't obeys ohms law because it only allows current to flow in one direction
• thermistors are used to detect temperature so as the temperature increases the resistance decreases. they are inversely proportional
• LDRs are used to detect light so their resistance decreases as light intensity increases
• current remains the same around the entire series circuit
• the pd adds across components in a series circuit to give the total
• resistance adds across the components to give the total resistance in a series circuit
• current is shared across the component branches in parallel (add to get the total)
• pd remains the same across all the branches in parallel