P2.4 Current Electricity Flashcards
How does a current flow?
When we out a metal wire in a circuit the cell creates a force on the free electrons in one direction. This causes the electrons to flow around the circuit
What is the current like in a series circuit?
Same everywhere
What component measures current?
Ammeter
How do you work out charge
Current X time
What do conductors have that mean the current can flow easily
Free electrons
Why do lamps light up?
When the current flows through the component the energy transfers to the component. The energy transfers to heat and the lamp gets so hot that it glows and some energy is transferred to light energy.
What measures voltage? What is voltage exactly?
Voltmeter
It compares the energy carried by the current leaving it. The change in current is due to electrical energy being transferred to other forms in the components
What does the energy transferred in a component depend on?
The potential difference
The charge that has flowed through the component
How do you work out the energy transformed?
Voltage X charge
What’s charge measured in?
Coulombs (C)
What is the current like in a parallel circuit?
The current is shared between the branches
How are voltmeters connected in a circuit?
In parallel to a component
What is voltage like in a series circuit?
It’s shared between components
What’s voltage like in a parallel circuit?
Same in every branch
Series circuit Parallel circuit
Current (1) (2)
Voltage (3) (4)
Fill in table
- Same
- Shared
- Shared
- Same
Why are lighting circuits in your home in parallel circuits?
Bulbs are bright - voltage is the same
If one breaks the others still light up
What things affect resistance?
Number of components
Type of metal
Cross-sectional area of the wire
What’s resistance measured in?
Ohms
can’t show you symbol :(
What’s the symbol for a fixed resistor in a circuit?
____
-| |-
—–
Basically a rectangle
What’s the total resistance in a series circuit?
The sum of all the individual resistances
What’s the relationship between voltage and current?
As voltage increases, the current increases but not as quickly
How do you calculate resistance?
Voltage / current
What’s the relationship between length of wire and resistance?
As the length of wire increases so does the resistance. The thinner the wire the bigger the resistance
What’s a diode?
Only lets current go in one direction - very high resistance in the other direction
look up graphs for bulb, resistor and diode - make sure you know them
(18th July 2016)
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:)
🤗👋🏽👍🏽
What’s the circuit symbols for LDR and a thermistor?
Look them up :,)
How does resistance in a thermistor change with temperature
As temperature increases, resistance decreases
How does the resistance of an LDR change with light intensity?
As lamp gets further away from the LDR the resistance increases
How do you work out charge?
Current X time
What’s the circuit symbol for a fuse?
A rectangle with a line through it
What’s the circuit symbol for a variable resistor
A rectangle with an arrow in it pointing north east
