Current Electricty II

Question 1

current =

Answer 1

rate of flow of charge

Question 2

current (units) =

Answer 2

Amps (A)

Question 3

Charge (coulombs) =

Answer 3

current (A) x time (s)

Question 4

voltage =

Answer 4

energy per unit charge

Question 5

voltage (units) =

Answer 5

Volts (V)

Question 6

1 joule per coulomb =

Answer 6

1 volt

Question 7

voltage (V) =

Answer 7

current (A) x resistance (Ω)

Question 8

energy (J) =

Answer 8

current (A) x time (s) x voltage (V)

Question 9

Current in a metallic conductor =

Answer 9

flow of negatively charged electrons

Question 10

LED can be used to indicate …

Answer 10

the presence of a circuit

Question 11

Describe how current varies in resistors, wires, filament bulbs and diodes.

Answer 11

• If you increase the resistance the current will decrease.
• Resistors, wires, filament bulbs and diodes all create resistance in a circuit and so the current will decrease
• This can be investigated using an ammeter and measuring the current with and without these components, or with different voltage levels (measured by voltage)

Question 12

Increasing the resistance will ….

Answer 12

decrease the current

Question 13

Decreasing the resistance will ,,,

Answer 13

increase the current

Question 14

Describe how illumination affects the resistance of an LDR and how temperature affects the resistance of a thermistor.

Answer 14

• An LDR is a light dependent resistor. Its resistance changes with the intensity of light. The brighter the light is, the less resistance; the less light MORE resistance
• Thermistors are temperature dependent resistors. In hot conditions, there will be less resistance, whereas in cold, the resistance is greater

Question 15

Resistance at constant temperature :

Answer 15

current flowing through the resistor at a constant temperature is directly proportional to the potential difference across it. A constant that gives a graph like this is said to follow Ohm’s law

Question 16

The filament lamp : Resistance

Answer 16

• Common type of light bulb
• Contains a thin wire called filament. This heats up when the electric current passes through it and produces light
• It doesn’t follow Ohm’s law
• Its resistance increases as the temperatures of its filament increases

Question 17

The Diode : Resistance

Answer 17

• Diodes are electronic components that can be used to regulate the p.d. In circuits and make logic gates
• LEDs give off lights and are often used for indicator lights in electrical equipment
• Has a very high resistance in one direction ; current can only flow in the other direction

Question 18

Design a circuit and experiment to investigate Current (I) – Voltage (V) characteristics.

Answer 18

1. Turn power supply up until the p.d. across the lamp is 12V
2. Record p.d. and current
3. Calculate resistance V = IR
4. Change voltage to see relationship