Measuring Electricity and Ohm's Law 6.2

Question 1

What is Current?

Answer 1

-Rate or speed which electrons flow in a circuit
-Unit: Ampere(A)
-Measured with ammeter
-Current can be either:
*Direct(DC): electrons flow in same direction, battery.
*Alternate(AC): electrons changes direction and 50 times every second, power points

Question 2

What is Voltage?

Answer 2

-Difference in charge between 2 points
-Measure of how much energy is supplied by energy source
-Unit: Volts(V)
-Measured with Voltmeter
-Broken circuit will not indicate any voltage

Question 3

What is the Voltage Supply?

Answer 3

-Australian power points supply 240V of energy
-Most appliances do not need 240V to function, phones 6V, laptop 19V
-Transformer used to reduce voltage for an appliance, faulty one could damage the appliance

Question 4

What is Resistance?

Answer 4

-Force opposes current
-Unit: Ohm(Ω)
-Measured with ohmmeter
-Electrons move along the circuit, their path is blocked by atoms of the circuit components, causes resistance
-The more components in circuit, the more resistance
-The lower the resistance the higher the current

Question 5

What are Wires Resistance?

Answer 5

-Resistance of wire depends on:
*Material: metals have low resistance, so most wires are made of copper
*Length: longer wires have more resistance
*Thickness: thicker wires are easier to pass through, less resistance

Question 6

What are Resistors?

Answer 6

-Reduce current flowing through in a circuit
-useful as too high current can damage electrical appliances
-Variable resistors allow change of resistance to control current, like controlling speed of motor or brightness of light bulbs

Question 7

What are Conductors?

Answer 7

-Metals are conductors, low resistance
-Copper is good and cheap, used for circuits
-Aluminum is excellent but expensive, used for high voltage transmission
-Metals like tungsten and nichrome are bad and give off thermal and light energy, used in light bulbs or heating elements

Question 8

What are Insulators?

Answer 8

Materials with high enough resistance to block flow of electrons
*Wood: Hold up power lines
*Rubbers and plastics: Coat wires prevent electricity from leaking out

Question 9

What is Ohm’s Law?

Answer 9

Formula:
I(current) = V
—
R
V = I times R
V
I R