Electrical Circuits and formulae

Question 1

Current

Answer 1

The flow of electric charge over time (s)
Unit is Ampere
Symbol I

Question 2

Voltage

Answer 2

Measure of the change of electrical energy
Unit is Volt
Symbol V

Question 3

Resistance

Answer 3

How hard it is for current to flow
Unit Ω Ohms
Symbol R

Question 4

Ohms Law

Answer 4

Resistance = voltage over current

Question 5

Parallel Circuit

Answer 5

More power was drawn resulting in more current. The volts were not divided and each thing on the circuit get the same amount.

Question 6

Series Circuit

Answer 6

Each thing got a share of the voltage so 6 volt between 3 bulbs becomes 2 volt per bulb. The amps stayed the same

Question 7

Ohms law rearrange

Answer 7

V=IR
I= V over R

Question 8

Combination Circuit

Answer 8

Both series and parallel combined

Question 9

Resistance Parallel

Answer 9

Rp 1/R1+1/R2

Question 10

Total Resistance

Answer 10

Rt=Rp+Rs

Question 11

Current Total

Answer 11

I = Vt/Rt

Question 12

Voltage (Series + Parallel)

Answer 12

V=Rs+Rp

Question 12

Current Parallel

Answer 12

I=V/R

Question 13

Voltage or Potential Dividers

Answer 13

Voltage is also known as Potential (Potential Energy Available in the circuit)
Combination circuits are used to split the voltage in a circuit to enable different parts of the circuit to get different voltage

Question 14

Rheostat Variable Resistor (Potentiometer)

Answer 14

Allows the resistance to be changed. Think volume knob on stereo or temperature knob on a stove.

Question 15

Power

Answer 15

Unit is Watt W
Power is the rate of energy charge over time
Power is also equal to the work done
△ = change in
Work = Energy charge = △E/t (FXD
Power is equal to work/time=voltage
P=VI or P=IV

Question 16

Ohms Law and Power

Answer 16

V=IR when you do not know the voltage
= P=(IR)XI
When you don’t know the current
= P=VX(V/R)

Question 17

Electric Charge and current

Answer 17

Electric Current is the flow of electric charge measured over a period of time by the number of electrons passing at a given point.
Current - Charge / Time
I=q/t
q = charge in coulombs (6X10^18 electrons)
Amperes (Amp) equals coulombs per second

Question 18

Electric Charge and Electric Field.

Answer 18

For electric charge to move there needs to be an electric field.
Electric field lines move from positive to negative
The lines have to be straight, evenly spaced out and the end lines have to curve

Question 19

Field lines around charges

Answer 19

Positive repel and negative attract
Strongest towards the centre and closer to the ion. Weak field on the edges

Question 20

Electric field strength

Answer 20

When a charge is in an electric field it experiences a force. The strength is given by
E= F/q
E= Electric Field Strength
F= Electric force
q= charge

Question 21

Electric Potential Energy

Answer 21

The energy a charge has within an electric field
△Ep=Eqd
Ep = charge in potential energy in potential energy J
E= electric field strength NC-1
q = charge in coulombs
d = △x = distance in M

Question 22

Electric Potential Difference

Answer 22

The potential energy difference stored per unit of charge.
Depends on the strength of the electric field (E) and he distance the charges moved
V=E/d

Question 23

Importance of electric Potential Difference

Answer 23

If electrical contact is made between 2 differently charged conductors will move from one to the other because there is a potential difference.
A coventiant zero point is the earth itself
Electrons flow to or from the earth until the object is neutral

Question 24

Potential Gradient

Answer 24

It is difficult to measure forces and charges in electrical situations much easier to measure voltage and distance giving us E =△V/△d = potential gradient in V m-1 It is a measure of the change in potential in the electric field as a charge moves over a distance.

Question 25

The size of a magnetic field

Answer 25

Magnetic Field B Distance d wire with current I Formula B=kI/d Where k is the proportionality constant in the relationship k=2X10-7 NA-2

Question 26

Magnets

Answer 26

Opposites attract Same Repel Magnetic fields go from N-S

Question 27

Magnetic Fields and wires

Answer 27

The magnetic field around a current when an electric circuit flows in a wire a magnetic field is set up around the wire. Several wires act as one and causes a greater magnetic effect

Question 28

Magnetic Fields and Wires Formula

Answer 28

Force = F Strength of Field = B Current = I Length of Wire = L Angle = Θ If angle between current and field the size of force is F=BILXSinΘ

Question 29

Magnetic Fields in a wire coil.

Answer 29

A solenoid is a wire coil. When an electrical current is introduced to the coil a magnetic field is created. The field has a north and south pole. the field is strongest in the middle. The strength of the field can be increased by increasing current and more coils.