Current Electricity

Question 1

Electric current

Answer 1

The flow of charge (Coulombs, C) or charged particles. When 1 C of charge flows past a specific point in one second, the current is 1 Amp (A).

Question 2

I = Q/t → Q = It

Answer 2

Current equals charge over time

Question 3

Potential difference

Answer 3

When 1 C of charge supplies 1 J of energy, the potential difference is 1 Volt

Question 4

Conventional current

Answer 4

Current flowing from a point of higher electrical potential to one of lower electrical potential. Electrons flow in the opposite direction

Question 5

Ammeters

Answer 5

Devices that measure current; they are always placed in series; they have negligible resistance and no potential difference

Question 6

Voltmeters

Answer 6

Devices that measure potential difference; they are always placed in parallel with a component; they have a very high resistance (10MΩ) and no current

Question 7

Resistance

Answer 7

Opposition to the flow of charge; measured in Ohms, Ω

Question 8

R = V/I

Answer 8

Resistance equals potential difference over current

Question 9

Kirchhoff’s First Law

Answer 9

The total current into any point in a circuit is equal to the total current out of that point; also called conservation of charge

Question 10

Conservation of charge

Answer 10

The total current into any point in a circuit is equal to the total current out of that point; also called Kirchhoff’s First Law

Question 11

Kirchhoff’s Second Law

Answer 11

The p.d. across the power supply is equal to the sum of the p.d.s across all the components in the circuit

Question 12

Poole’s Law of p.d.

Answer 12

Any two points in a circuit connected only by a lead are at the same electrical potential

Question 13

Power

Answer 13

The rate at which energy is transformed from one form to another; measured in Watts, W

Question 14

Power = …

Answer 14

P = VI = I² R = V² / R

Question 15

For resistors in series, R = …

Answer 15

R = R₁ + R₂

Question 16

For resistors in parallel, 1 / R = …

Answer 16

1 / R = 1 / R₁ + 1 / R₂

Question 17

For two resistors in parallel, R = …

Answer 17

R = Product / Sum [only works for two resistors]

Question 18

Ohm’s Law

Answer 18

For an Ohmic conductor, the potential difference across the ends of the conductor is directly proportional to the current passing through it, providing the temperature of the conductor remains constant

Question 19

Ohmic conductor

Answer 19

A conductor with constant resistance; a component where V ∝ I providing the temperature is constant

Question 20

Semiconductor diode

Answer 20

A component that only allows current to flow in forward bias. Resistance is infinite in reverse bias, and starts to decrease at +0.6-0.7 V