🪫 • Lesson 3.6 : Electricity and Magnetism (Phys)

Question 1

What are the forces between magnetic poles and magnets?

Answer 1

Like poles repel (N-N, S-S), opposite poles attract (N-S).

Magnetized materials have aligned magnetic domains; unmagnetized materials don’t.

Question 2

What is a magnetic field?

Answer 2

A magnetic field is a region where a magnetic pole experiences a force.

Question 3

How is the direction of a magnetic field defined?

Answer 3

The magnetic field direction at a point is the direction of the force on the N pole of a magnet at that point.

Question 4

What is the difference between temporary and permanent magnets?

Answer 4

Temporary magnets (made of soft iron) lose magnetism easily, while permanent magnets (made of steel) retain their magnetism.

Question 5

What is induced magnetism?

Answer 5

Induced magnetism occurs when a material becomes magnetic due to the influence of a nearby magnet.

Question 6

What is the difference between magnetic and non-magnetic materials?

Answer 6

Magnetic materials are attracted to magnets (ex. iron), while non-magnetic materials are not (ex. wood, plastic).

Question 8

How does a permanent magnet differ from an electromagnet?

Answer 8

A permanent magnet is always magnetized, while an electromagnet’s magnetism is controlled by an electric current.

Question 9

What are positive and negative charges?

Answer 9

Positive and negative charges are opposites.
Like charges repel, and opposite charges attract.

Question 10

How is charge measured?

Answer 10

Charge is measured in coulombs (C).

Question 11

How do charges interact?

Answer 11

Positive charges repel other positive charges, negative charges repel other negative charges, and positive charges attract negative charges.

Question 12

What is an electric field?

Answer 12

An electric field is a region where an electric charge experiences a force.

Question 13

How does electrostatic charging by friction work?

Answer 13

When electrons are transferred between materials, making one object negatively charged and the other positively charged.

(To check if an object is charged, see if it attracts small objects like paper).

Question 14

How is the direction of an electric field defined?

Answer 14

The direction of an electric field is the direction of the force on a positive charge at that point.

Question 15

What happens when solids are charged by friction?

Answer 15

Charging by friction only transfers negative charge (electrons).

Question 16

What’s the difference between conductors and insulators?

Answer 16

Conductors allow electric charge to flow (ex. metals), while insulators do not (ex. rubber, plastic).

Question 17

What is electric current?

Answer 17

Electric current is the flow of charge, measured as the charge passing a point per unit time.
Formula: I = q/t

Question 18

What is the relation between electric current and metals?

Answer 18

In metals, electric current is the flow of electrons.

Question 19

How do electrons move in metals to conduct electricity?

Answer 19

In metals, conduction happens as delocalised (mobile) electrons move through the material.

Question 20

What are ammeters used for?

Answer 20

Ammeters measure electric current, and can be analogue or digital with various ranges.

Question 21

What is conventional current?

Answer 21

Conventional current flows from positive to negative, but electrons actually flow from negative to positive.

Question 22

What’s the difference between a.c. and d.c.?

Answer 22

Alternating current (a.c) changes direction periodically.

Direct current (d.c.) flows in one direction.

Question 23

What causes current in a circuit?

Answer 23

The voltage of the source causes current to flow in the circuit.

Question 24

What is electromotive force (e.m.f.)?

Answer 24

E.m.f. is the electrical work done by a source to move a unit charge around a complete circuit.
Measured in volts (V).

Question 25

How is voltage shared in a series circuit?

Answer 25

In a series circuit, the voltage of the source is *shared between the components.*

Question 26

What is potential difference (p.d.)?

Answer 26

P.d. is the work done by a unit charge passing between two points in a circuit. Measured in volts (V).

Question 27

What are voltmeters used for?

Answer 27

Voltmeters measure **potential difference**, and can be analogue or digital with different ranges.

Question 28

What is the equation for resistance?

Answer 28

R = V/I Where R is resistance, V is voltage, and I is current.

Question 29

What does the current–voltage graph of a resistor look like?

Answer 29

The graph is a **straight line** for a resistor with constant resistance, showing that current is directly proportional to voltage (Ohm’s law).

Question 30

How do you determine resistance using a voltmeter and ammeter?

Answer 30

Measure the voltage across the resistor using a voltmeter and the current through it using an ammeter. Then calculate resistance using R = V/I.

Question 31

How is resistance related to length in a metallic conductor?

Answer 31

Resistance is **directly proportional** to the length of the conductor.

Question 32

How is resistance related to cross-sectional area in a metallic conductor?

Answer 32

Resistance is **inversely proportional** to the cross-sectional area of the conductor.

Question 33

How do electric circuits transfer energy?

Answer 33

Electric circuits transfer energy *from a source* (like a cell or mains supply) *to components in the circuit*, and then to the *surroundings* (as heat, light, etc.).

Question 34

What is the equation for electrical power?

Answer 34

P = IV Where P is power, I is current, and V is voltage.

Question 35

Where is the equation for electrical energy?

Answer 35

E =IVt Where E is energy, I is current, V is voltage, and t is time.

Question 36

What is a kilowatt-hour (kWh)?

Answer 36

A kilowatt-hour is the energy used by a 1000-watt appliance running for one hour. (To calculate cost; multiply energy used (in kWh) by the rate per kWh).