Topic 3

Question 1

Resistance

Answer 1

the property of a substance that hinders motion of electric charge and converts electric energy into other forms of energy. Measured in Ohms and using an ohmmeter( or multi-meter)

Question 2

How to calculate resistance

Answer 2

R = V/I
I = V/R
V = IR

Question 3

Resistors

Answer 3

Used to control current or voltage to suit the specific needs of other electrical devices in the circuit.
Usually made of heat conducting ceramic coated with materials like carbon, zinc or resistance wire.

Question 4

Variable resistors

Answer 4

• do not have a fixed resistance, instead their resistance changes in response to temp, light, voltage or some other variable

Question 5

Types of circuit

Answer 5

Series- one pathway, shared voltage, equal current

Parallel- multiple pathways- equal voltage for each load, current is slowed after each load

Question 6

House wiring

Answer 6

• Practical circuits are parallel, because turning on one load will not reduce the amount of electricity going to the other, and turning off one load will not turn off the whole circuit
• One problem is too many things on at once,this increases the current and can cause overheating and electrical fires
• We use fuses or circuit breaker to prevent this

Question 7

Copper wires

Answer 7

-Very good conductors, but have slight resistance
- AWG( american wire gauge)
Thicker(lower number) is less resistant
Thinner(higher number) is more resistant

Question 8

Factors effecting wire resistance

Answer 8

Length( increases with length)
Cross sectional area( decreases with area)
Temperature( increases with temp)
Material( depends on material and atoms)