Physics Chapter 13 - Electrical Systems

Question 1

Define electric current

Answer 1

An electrical current is the rate of flow of electrical charge.

Question 2

What is the direction of conventional current and electron flow.

Answer 2

Conventional current flow: Negative side of battery to positive side.

Electron flow: Positive side of battery to negative side.

Question 3

What is S.I. unit and symbol of electric current

Answer 3

S.I. Unit: ampere
Symbol: A
(e.g. I=3A)

Question 4

Electricity is a form of ______

Answer 4

Energy

Question 5

What instrument can measure current

Answer 5

Ammeter

Question 6

What is potential difference across a conductor in a circuit
(Define)

Answer 6

The potential difference between the two points of a circuit component is a measure of the amount of potential energy that is changed into other forms of energy when an electron passes between the two points.

Question 7

What is the S.I. and symbol for potential differences

Answer 7

S.I. unit: volt

Symbol: V

Question 8

What is the property of a material that restricts the flow of electrical current

Answer 8

Resistance

Question 9

What is the S.I. unit and symbol of resistance

Answer 9

S.I. unit: ohm

Symbol: Ω

Question 10

Why is copper commonly used to make wires

Answer 10

Copper has low electrical resistance and it allows electric current to flow through easily, and it is much lower in price.

Question 11

Describe how a rheostat works in a light dimmer.

Answer 11

When the rheostat in the light dimmer is adjusted to its maximum resistance, the amount of current flowing through the lights would be the smallest. Thus, the lights would all be at their dimmest.
When the rheostat in the light is adjusted to its lowest resistance, the amount of current flowing through the lights would be the greatest. Thus, the lights would be at their brightness.

Question 12

How will adding resistors in series be different from adding resistors in parallel.

Answer 12

Adding another resistor in parallel decreases the resistance in the circuit. Hence, the current flowing through the light bulb increases. The light bulb becomes brighter.

Adding another resistor in series increases the circuit. Hence, the current flowing through the light bulb decreases. The light bulb becomes dimmer.

Question 13

What are the effects of electric currents

Answer 13

• chemical effect
• magnetic effect
• heating effect
• lighting effect

Question 14

Define Ohm’s law

Answer 14

States that the ratio between the voltage across the ends and the current flowing through the conductor is constant

Question 15

Define resistance

Answer 15

Resistance of a conductor is defined as the ratio of potential difference(V) across the conductor and current(I) flowing in it.

Question 16

What is the equation of Ohm’s Law

Answer 16

R = V/I
Resistance = Potential difference / current

Question 17

What happens when a wire is frayed and damaged? What precautions should be taken?

Answer 17

Insulation around the wire is worn out. The person who touches it will get an electric shock. Replace the damaged wire with a brand new one

Question 18

Name 3 advantages of using an electromagnet

Answer 18

1) It can be temporarily turned off
2) Polarity can be changed
3) Can adjust strength of magnet