Topic 5- Electricity

Question 1

explain the term static electricity

Answer 1

• most objects have almost exactly the same number of protons and electrons ( neutral)
• when an object gains extra electrons, it becomes negatively charged
• when an object loses electrons it becomes positively charged

Question 2

how are voltmeter and ammeters connected to a circuit?

Answer 2

* A voltmeter is connected in parallel with a device to measure its voltage, while * an ammeter is connected in series with a device to measure its current.

Question 3

conventional current

Answer 3

conventional current flows from positive to negative

Question 4

electron flow

Answer 4

electrons flow from negative to positive

Question 5

how do you calculate resistance from an I-V graph and a V-I graph?

Answer 5

* R= V/I * resistance is measured in ohms

Question 6

how does the current change in a circuit if the resistance changes and/ or the voltage changes?

Answer 6

• Changing the voltage - If you increase the voltage across a component, there will be more current through the component. Too high a voltage and the bulb will blow.
• Changing the resistance - If you increase the number of lamps in a series circuit, there will be less current. The lamps resist the current, so if you put more lamps into the circuit, there is more resistance.

Question 7

how does the resistance vary when a current flows thorough a filament bulb?

Answer 7

The current flowing through a filament lamp is not directly proportional to the voltage across it

Question 8

state Ohm’s Law

Answer 8

Current is directly proportional to voltage (if temperature is constant)

Question 9

give the definition of current

Answer 9

the amount of charge flowing in 1 sec.

Question 10

give the definition of voltage

Answer 10

the electrical energy difference for 1 coulomb of charge

Question 11

what happens to like and opposite charges

Answer 11

like charges repel. Unlike charges attract.

Question 12

understand the layout of a mains plug and the importance of fuse and earth wire

Answer 12

fuse - protects the appliance and protects against fires. It breaks if the current gets too high.

earth wire - protects the user by providing an easy route for electricity to travel to Earth. ( if the case if plastic no earth wire is needed)

Question 13

give the definition for insulator

Answer 13

a substance or device which does not readily conduct electricity

Question 14

give the definition for conductor

Answer 14

a material or device that conducts or transmits heat or electricity

Question 15

what are the properties of a thermistor?

Answer 15

As temp increases, the resistance decreases.

Question 16

what’s the link between energy and voltage?

Answer 16

The electrical potential energy increases as the voltage increases. Voltage shows us the difference of the electrical potential energy/ coulomb