P4: Electricity Flashcards
What must be included for an electric charge to flow through a circuit?
A source of potential difference
What does the current through a component depend on?
The resistance of the component and the potential difference across the component
What is the relationship between current and resistance for a given potential difference?
The greater the resistance, the smaller the current
What is the relationship between the current and the potential difference through an ohmic conductor?
The current is directly proportional to the potential difference (meaning resistance is constant)
Describe the resistance in components such as lamps, diodes, thermistors and LDRs
It changes with the current through the component
In the IV graph for a diode, why is it zero at the beginning?
Because it has a very high resistance in the reverse direction
Describe the relationship between the resistance and the temperature in a thermistor
The resistance decreases as the temperature increases
Describe the relationship between the resistance and the light intensity in an LDR
The resistance decreases as the light intensity increases
State 3 things about components connected in series
Same current throughout, total potential difference is shared between components and total resistance is the sum of all the resistances
State 3 things about components connected in parallel
Same potential difference throughout, total current is the sum of all the currents and total resistance is less than the smallest resistance
When a polythene rod is rubbed with a cloth, which material loses electrons?
The cloth
When an acetate rod is rubbed with a cloth, which material loses electrons?
The acetate rod
What causes sparks?
The potential difference between the earth and the object increases when an electric charge is produced. If the voltage gets large enough, the electrons can jump across the gap between the charge object and earth, causing a shock
In an LDR, what is the relationship between resistance and light intensity?
The higher the light intensity, the lower the resistance
What are 2 features of an LED?
Allows current to flow in one direction and emits light when current flows
