(P2)Electricity And Circuits Flashcards
Revise circuit symbols
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Describe a series circuit and a parallel circuit
A series circuit contains just one loop, around which an electric current can flow. A parallel circuit contains more than one loop, and the current with split up or recombine at the junctions
Describe the differences for current and potential difference in series and parallel circuits
Series: current the same at all points. Pd across components (voltmeters) add to equal pd in cell
Parallel: current splits at junctions. Pd in across each branch is same as pd across cell
Why are Xmas tree light connected in a parallel circuit?
Because in a series, if one bulb breaks the current can’t flow, so the rest of the lights will go out
What is an electric current?
How do you calculate current?
The rate of flow of charge.
Current = charge / time
How do you calculate energy transferred?
Charge moved x potential difference
What is the resistance of a component?
How can the resistance be changed?
A way of measuring how hard it is for electricity to pass through it (ohms.
By using resistors or a variable resistor in the circuit
If the resistance goes up, what happens to the current?
It goes down
What’s does Ohm’s law state?
What is the equation for Ohm’s law?
That the size of the current flowing through a resistor is directly proportional to the potential difference across the component.
Pd= current x resistance
What do the I-V graphs of a fixed resistor, a filament lamp and a diode look like?
FR - straight diagonal
FL - f shape
D - flat, then bends
If there is a high light intensity, what happens to light dependent resistors?
If there is a high temperature what happens to thermistors?
The resistance goes down for both LDRs and thermistors
How can unwanted thermal energy transfers in resistors be reduced?
By using low resistance wires (better conductors/ shorter/ thicker). This will waste less energy
How is thermal energy made in circuits?
When electron and ions collide with each other in the lattice, they make kinetic energy which is dissipated as thermal energy
What is power?
How do you calculate it?
The rate at which energy is transferred (watts)
Current x pd
What is a direct current?
When the electrons in a current all flow in the same direction. The current supplies by cells and batteries is direct.
