current electricity, dc circuits, practical electricity

Question 1

An electric current is…

Answer 1

An electric current (I) is the rate of flow of electric charge Q

Question 2

How are current and charge related?

Answer 2

I = Q/t, where I = current (A), Q = charge (C) and t = time (s)

Question 3

Electromotive force of an electric energy source is…

Answer 3

Electromotive force of an electric energy source is the work done by source in driving a unit charge around a complete circuit

Question 4

How is e.m.f and work done related?

Answer 4

e = W/Q, where e = emf (V or j/c), W = work done (J) and Q = charge (C)

Question 5

Potential difference across a component in an electric current is…

Answer 5

Potential difference across a component in an electric current is the work done to drive a unit charge through the component

Question 6

How is PD and work done related?

Answer 6

V = W/Q

Question 7

Resistance of a component is…

Answer 7

Resistance of a component (R) is the ratio of the potential difference V across it to the current I flowing through it

Question 8

R = ?

Answer 8

R = V/I, where R = resistance of component (ohms), V = p.d. across the component (V), and I = current flowing through the component (I) (V = RI)

Question 9

Resistance of a wire?

Answer 9

R = pl/A, where R = resistance (ohms), l = length (m), A = cross sectional area (m^2)

Question 10

Current, potential difference, resistance in series circuit?

Answer 10

I = I1 = I2 =… (Same current flows through circuit components)
V = V1 + V2 +…
R = R1 + R2 +…

Question 11

Current, potential difference, resistance in parallel circuit?

Answer 11

I = I1 + I2 +… (current splits into diff branches)
V = V1 = V2… (pd across whole circuit is equal to pd across each resistor)
1/R = 1/R1 + 1/R2 +… (reciprocal of Reff is sum of reciprocal of all individual resistances)

Question 12

Potential divider is…

Answer 12

A potential divider is a line of resistors connected in series. (It is used to provide a fraction of the voltage of a source to another part of the circuit.)

Question 13

Vout =

Answer 13

Vout = R2/R1+R2 x V

Question 14

What are 2 examples of input transducers

Answer 14

Thermistor (resistance decrease as temp increase), light dependent resistor (LDR) (resistance decrease as light increase)

Question 15

What are the four formulas for power

Answer 15

P = E/t
P = VI
P = V^2/R
P = I^2/R
P = power (W)
E = energy (J)