P4

Question 1

cell
battery
lamp
ammeter

voltmeter 
fixed+ variable resistor 
light + light emitting diode 
fuse 
switcg

Answer 1

• converts stored chemical energy into electrical potential energy
• source of energy which provides a push
• bulb uses the electrical energy provided by the battery, but does not use current.
• instrument for measuring either direct or alternating electric current
• measures the difference in electrical potential between two points in an electric circuit.
• restrict current flow in a circuit - resistance that does not change , variable resistor is used in some dimmer switches and volume controls.
• a semiconductor diode which glows when a voltage is applied
• fuse breaks the circuit if a fault in an appliance causes too much current to flow
• switch serves the purpose of controlling the flow of electrical current

Question 2

difference between a battery and a cell

Answer 2

A cell is a single unit device , A battery is either a primary battery or a secondary battery meaning it is rechargeable or non-chargeable.

Question 3

what is current and how is it measured ?

Answer 3

measured in amperes - Current is a measure of how much electric charge flows through a circuit

Question 4

why are metals good conductors of electricity

Answer 4

because the atoms in the metals form a matrix through which outer electrons can move freely

Question 5

which way does current flow

Answer 5

Electrons flow from the negative terminal to the positive

Question 6

what are the units for charge

Answer 6

coulomb (C)

Question 7

what is the equation that links charge , flow , current and time

Answer 7

Energy transferred = power x time.

Question 8

what is potential difference and how is it measured

Answer 8

Potential difference is measured using a device called a voltmeter

the difference of electrical potential between two points

Question 9

what is resistance ? what unit are they

Answer 9

Resistance is a measure of the opposition to current flow in an electrical circuit , measured in ohms

Question 10

explain how and why resistance changes in a long wire compared to a short wire

Answer 10

The resistance of a long wire is greater than the resistance of a short wire because electrons collide with more ions as they pass through.

Question 11

explain how and why resistance changes in a thin wire compared to a thick wire

Answer 11

The resistance of a thin wire is greater than the resistance of a thick wire because a thin wire has fewer electrons to carry the current

Question 12

resistance formula

Answer 12

resistance = voltage
————
current

Question 13

what is ohms law

what is an ohms conductor

Answer 13

Ohm’s Law state that the voltage across a conductor is directly proportional to the current flowing through it,
an ohmic conductor

Question 14

give the use of a light dependant resistor and thermistor

Answer 14

light-dependent resistors are used to detect light levels

Thermistors are used as temperature sensors

Question 15

draw a series circuit

Answer 15

A series circuit is one loop; all electrons in that loop form one current. An ammeter will measure it

Question 16

whats the rule for current in a series circuit

Answer 16

The amount of current is the same through any component in a series circuit.

Question 17

give the rule for potential difference in a series circuit

Answer 17

The total potential difference supplied by the cell is divided up between the components.

Question 18

give the rule for cells in a series circuit

Answer 18

The total resistance of a series circuit is equal to the sum of individual resistances

Question 19

whats the equation for calculating total resistance in a series circuit

Answer 19

R1 + R2 + R3.

Question 20

the rule for current in a parallel circuit

Answer 20

A parallel circuit has two or more paths for current to flow through. Voltage is the same across each component of the parallel circuit. The sum of the currents through each path is equal to the total current that flows from the source.