physics 4

Question 1

What is electric current?

Answer 1

rate of flow of charge

Question 2

What units are charge, current, and time measured in?

Answer 2

coulombs (C), amperes (A), seconds (s) respectively

Question 3

What is the same at all points when charge flows in a closed loop

Answer 3

current

Question 4

What must there be in a closed circuit so that electrical charge can flow?

Answer 4

For electrical charge to flow through a closed circuit the circuit must include a source of potential difference (p.d.)

Question 5

Which two factors does current depend on and what are their units?

Answer 5

resistance in ohms (Ω), p.d. in volts (V)

Question 6

What happens to the current if the resistance is increased but the p.d. stays the same?

Answer 6

current decreases

Question 7

What is an ohmic conductor?

Answer 7

conductor where current is directly proportional to the voltage so resistance is constant (at constant
temperature)

Question 8

What happens to the resistance of a filament lamp as its temperature increases?

Answer 8

resistance increases

Question 9

What happens to the resistance of a thermistor as its temperature increases?

Answer 9

resistance decreases

Question 10

What happens to the resistance of a light-dependent resistor when light intensity increases?

Answer 10

resistance decreases

Question 11

What are the main features of a series circuit?

Answer 11

same current through each component, total p.d. of power supply is shared between components, total resistance of all components is the sum of the resistance of each component

Question 12

What are the main features of a parallel circuit?

Answer 12

p.d. across each branch is the same, total current through circuit is the sum of the currents in each branch – total resistance of all resistors is less than the resistance of the smallest individual resistor