Coulomb's Laws

Question 1

What three key things did Charles Coulomb discover?

Answer 1

• The force between objects is directly proportional to their product
• The force of attraction and distance apart are inversely proportional
• The size of charge increases the amount of attraction/repulsion and the further the distance the weaker the charge

Question 2

1 Coulomb represents:

Answer 2

6.24 x 10¹⁸ e moving.

Question 3

State Coulomb’s equation. What does it help us find?

Answer 3

F = Q₁Q₂/d²

Finds the force between to charges (proton (Q1) near electron (Q2). d is the distance between the two charges,

Question 4

What is electron flow and conventional current? Which is used and why?

Answer 4

Electron Flow: the movement of electrons in a completed circuit is from the neg to pos side

Conventional Current: opposite to electron flow, used to eliminate negative values.

In most cases, the flow of negative electrons (electron flow) causes electrical current. However, mathematically, dealing with electrons is inconvenient so we treat current as the flow of positive charges.

Question 5

What is voltage and what formula is used?

Answer 5

Voltage is the change in energy through a load:

V = E/Q, energy per charge

Question 6

What is current and what formula is used calculate it?

Answer 6

Current is the amount of charge that passes by a load per second.

I = Q/t, charge per second

Question 7

What is resistance and what formula is used to calculate it?

Answer 7

Resistance is the degree of difficulty an electron has passing through a load.

R = V/I

Question 8

State the four factors that affect resistance in a conductor

Answer 8

1. Length – resistance is directly proportional to the length of the conductor
   
   1. The longer the conductor the higher the resistance
2. Cross-Sectional Area – resistance is inversely proportional to the cross-sectional area
   
   1. Increasing the width of the conductor decreases resistance running through it
3. Type of Material – resistivity is a property of a material; it is the degree that the material resists the flow of electrons
   
   1. Metals have low resistance (good conductors), non-metals have high resistance (crappy conductors)
4. Temperature – resistance is not directly proportional to the temperature, but increases with temperature
   
   1. Superconductors: below certain temperatures, these conductors have a resistance of 0.

Question 9

What is electrical potential energy?

Answer 9

When you put a positive and negative charged object close together, it takes work to keep them apart, creating potential energy. As this potential energy meets up with loads in a circuit, the resistance causes a loss of potential energy – it is transferred to the load instead.

Question 10

What is electrical potenial difference?

Answer 10

Potential difference is what we measure using voltmeters; it is the amount of voltage being used up in a circuit.

Question 11

What is electrical power? State its 3 equations!

Answer 11

Power is the rate of energy consumption per second: P = E/t. Symbol is P, unit is Watts.

1. P = IV
2. P = V²/R
3. P = I²R