Electricity - Charge, Current And PD

Question 1

What must the circuit have for electrical charge to flow through

Answer 1

A closed circuit must include a source of P.D

Question 2

What is current

Answer 2

A flow of electrical charge. The size of the electric current is the rate of flow of electrical charge. Charge flow = current x time

A current has the same value at any point in a single loop

Question 3

What does the current through a component depend on?

Answer 3

Depends on both the resistance of the component and the P.D across component. Greater resistance, smaller the current for a given P.D across the components

Question 4

What is P.D, current and resistance measured in

Answer 4

P.d - volts
Resistance - ohms
Current - amps

Question 5

Current through ohmic conductor

Answer 5

The current through a ohmic conductor at a constant temperature is directly proportional to the p.d across the resistor. This means that the resistance remains constant as the current changes.

Question 6

Resistance in a filament lamp

Answer 6

The resistance of the filament lamp increases as the temperature of the filament increases.

Resistance of component ; lamps, diodes, thermistors and LDRS is not constant. It changes with the current through the component.

Question 7

Current through a diode

Answer 7

Current through a diode flows in one direction only. The diode has a very high resistance in the reverse direction.

Question 8

Resistance of a thermistor and LDR

Answer 8

R of thermistor decreases as the temperature increases.
R of LDR decreases as the light intensity increases.

Question 9

In bright light what happens to the LDR?

Answer 9

The resistance of the LDR decreases, allowing more current to pass through. In dark - resistance increases reducing the current flow.
LDR used - automatic night lights, outdoor lighting and burglar detectors

Question 10

What can thermistors be used for

Answer 10

Temperature detectors, car engine sensors, electronic thermostats

Question 11

How can you give negative values for current and potential difference

Answer 11

Reverse the cell

Question 12

How would you place an ammeter and a voltmeter into a series circuit?

Answer 12

Ammeter - in series with the resistor
Voltmeter - in parallel with the resistor

Question 13

How do u measure uncertainty

Answer 13

You find the range and then divide it by two. Eg three numbers - 100, 200, 150. Range - 100, uncertainty - 50