(5.1) - Current Electricity

Question 1

What is Current?

Answer 1

• The rate of flow of charge

Question 2

What is Voltage / Potential Difference

Answer 2

Driving force that pushes current through a circuit

Work done per unit charge

Question 3

What is Ohm’s Law?

Answer 3

I ∝ V, but only if other physical conditions remain constant

Question 4

Describe energy transfers that happen in a simple circuit with a light bulb and a battery

Answer 4

1. Energy is stored in battery as chemical
2. Chemical -> Kinetic to electrons
3. Electrons collide with fixed positive ions in the wire, Ions store it as Kinetic, causing them to vibrate more, and transfers to surrounding as heat
4. Electrons collide with ions in filament, transfers energy to filament. Bulb transfers energy to surroundings via light and dissipates as heat.

Question 5

How many electrons in 1 Coulomb

Answer 5

1 / 1.6 * 10 ^ -19 = 6.25 * 10 ^ 18

Question 6

I = Q / t. Explain how to calulate Q without rearrganging equation (total charge) (use external equations)

Answer 6

Q = number of electrons * charge of electron

Question 7

What is Conventional Current?

Answer 7

Flow of positive charge (positive to negative)

Old ideology, we now know this isn’t true.

Question 8

What is Electron Flow?

Answer 8

Flow of negative charge (negative to positive)

Question 9

Why is copper used for wires?

Answer 9

Low resistance

Question 10

Describe the current-voltage characteristics of an ohmic conductor (resistor)

Answer 10

• Linear relationship (directly proportional)

Question 11

Describe the current-voltage characteristics of a semiconductor diode

Answer 11

• Non-linear with a threshold
• Below threshold voltage, current is very small
• Above threshold voltage, current increases rapidly

Question 12

Describe the current-voltage characteristics of a filament lamp

Answer 12

• Non-linear due to increasing resistance
• Beginning, correlation between current and voltage
• As current flows, filament heats up, increases resistance andcurrent slows down

Question 13

Also why is copper used

Description of the qualitative effect of temperature on the resistance of metal conductors

Answer 13

• Metal is heated, resistance increases
• Copper is used because it is a good electrical conductor, meaning less resistance, so less heat build up

Question 14

Description of the qualitative effect of temperature on the resistance of thermistors.

Answer 14

Resistance decreases as temperature increases