09. P4 Electric Circuits

Question 1

What charge does an electron have?

Answer 1

negative

Question 2

What does a cell do in a circuit?

Answer 2

Provides energy to the charge flowing through it.

Question 3

On a cell/battery symbol, which line represents the positive terminal?

Answer 3

longer line

Question 4

What does a resistor do in the circuit?

Answer 4

It resists the flow of the current through it, energy is transferred into heat energy

Question 5

What is the energy change taking place in a battery/cell?

Answer 5

Chemical into electrical and heat

Question 6

What is the direction of conventional current?

Answer 6

Travels from positive to negative terminal

Question 7

What direction does the electrons flow in a circuit when connected?

Answer 7

Electrons flow from negative terminal to the positive terminal

Question 8

What does a bulb do in the circuit?

Answer 8

Converts electrical energy into light and heat energy

Question 9

What does a diode do?

Answer 9

It only allows current to flow in one direction

Question 10

What device is used to measure the current in a circuit?

Answer 10

Ammeter

Question 11

What is an LDR?

Answer 11

Light Dependent Resistor = device whose resistance decreases as more light shines on it

Question 12

What is a thermistor?

Answer 12

Device whose resistance decreases as temperature increases

Question 13

What device can be added to a circuit to allow the used to alter the current flowing in a circuit?

Answer 13

Variable Resistor

Question 14

What is the purpose of a voltmeter?

Answer 14

It is used to measure the potential difference across a device

Question 15

How can thermistors be used in a device?

Answer 15

Temperature sensor

Question 16

How can a LDR be used in a device?

Answer 16

Light level sensor

Question 17

What happens to the resistance of a thermistor when the temperature increases?

Answer 17

Resistance decreases

Question 18

What happens to the resistance of a LDR when the light level increases?

Answer 18

Resistance decreases

Question 19

Rule for current measurement in a series circuit?

Answer 19

Current is the same at any point in the circuit

Question 20

Rule for current measurement in a parallel circuit?

Answer 20

Current leaving the battery splits between each of the branches in the circuit (Battery current = A1 + A2+ A3…)

Question 21

What is electric charge measured in?

Answer 21

Coulombs

Question 22

What is the symbol used for electric current?

Answer 22

Q

Question 23

What is the symbol used for coulombs?

Answer 23

C

Question 24

What are the units of resistance?

Answer 24

Ohms

Question 25

State what is meant by resistors obeying Ohm's law?

Answer 25

At a constant temperature, the current through a resistor is directly proportional to the voltage across it

Question 26

Name a component which is said to be an ohmic conductor?

Answer 26

Resistor

Question 27

In an I-V graph, a steep line(high gradient) indicates what about the component being tested?

Answer 27

High gradient = low resistance

Question 28

Explain the curved feature of the IV plot of a filament lamp?

Answer 28

As the PD increases, the current increases,causing the temperature to increases so the resistance increases.

Question 29

Why is the diodes IV plot a flat horizontal line along the X-axis in the reverse direction?

Answer 29

Because the resistance is very high in reverse direction, as it only allows current to flow in one direction.

Question 30

At what PD across a diode in the forward direction, does the current start to flow?

Answer 30

0.6V

Question 31

What happens to the PD of the battery in a series circuit?

Answer 31

The PD is shared across each of the components

Question 32

What determines the share of the PD across components in a series circuit?

Answer 32

The resistance, a component with a higher resistance compared to the others will have a bigger share.

Question 33

What is the total resistance in a series circuit equal to?

Answer 33

For a series circuit, the total resistance is equal to the sum of all the components resistors in the circuit

Question 34

What happens to the PD of the battery in a parallel circuit?

Answer 34

The PD over the battery is the same as the PD over each of the branches in the parallel circuit.

Question 35

What happens to the total resistance when you add more resistors in parallel?

Answer 35

The total resistance decreases

Question 36

What are the requirements for a static charge to buildup on an object? PHYSICS ONLY

Answer 36

Friction between two insulators, electrons transfer from one object to another.

Question 37

Explain in terms of electrons why a polythene rod becomes negatively charged when rubbed with a dry cloth… PHYSICS ONLY

Answer 37

Electrons transfer from the surface atoms of the cloth to the rod so the rod becomes negatively charged