Electricity Flashcards
Rule of thermistors
T emperature
U p
R esistance
D own
Rule of light dependant resistors
L ight
U p
R resistance
D own
Electrical current
Electric current is the rate of flow of charge (Q) (coulombs)
ACDC
Alternating current - produces a flow that reverses in direction many times per second
direct current - produces a flow of charge in one direction
Relationship:
Voltage in series
Divides
VT= V1 + V2 + V3
Relationship:
Current in series
Current in series is equal
IT = I1+ I2 + I3
Resistance in series
Divides
RT = r1+r2+r3
Voltage parallel
Equal
Vt= v1 = v2 = v3
Current in parallel
Divides
It= I1+ i2 + i3
Resistance in parallel
Decreases as no. Of branches increase
1/Rt = 1/R1 + 1/r2 + 1/r3
Transistor
A voltage controlled switch
Different kinds of transistors
NPN - 0.7v or greater (switch on at)
MOSFET - 2v or greater
Electric field
Region of space where force is felt
What are electric fields caused by
Charges repelling and attracting
Like charges repel - electron to electron
Opposite charges attract - electron to proton
Voltage
Joules per coulomb of charge
Where does voltage come from?
Where do we find this?
The electric field supplies energy to the charges
Electric field provided by the power supply
How do you calculate the voltage across resistors in a voltage divider circuit?
- Apply ohms law
- once to whole circuit for current
-then to individual resistor
Or - Use Eq.
V1/vt = r1/rt
Power
Power is the energy used per second
What can’t led’s do??
To solve?
Can’t allow too much current to pass through
Place in series with a resistor
To make sure current flows - place arrows downwards negative part of supply as it only allows current to flow in one direction
When temperature of conductor is increased?
Resistance increases
Current decreases
Ammeter must be connected in
Series
Voltmeter connected in
Parallel
Resistance
Measure of how much a component or circuit opposed the flow of current
Bigger the resistance
Smaller current
Voltage increases
Current increases in direct proportion
