Current Electricity

Question 1

What is the difference between conductors and insulators?

Answer 1

In general metals are conductive. This is due to their regular lattice structure of ions and free electrons which are free to move and carry a charge.

Non metals lack free electrons and are locked in the bonding process, so do not move and carry charge.

Question 2

What is current?

Answer 2

Current is the result of electrical charge on the move, in wires it is carried by negative electrons. It moved from negative to positive or opposite the conventional current.

Question 3

What is current measured in? And what is true about current when in a series circuit?

Answer 3

Current is measure in amperes and is the same at every point in a series circuit.

Question 4

What is true about current in a parallel circuit?

Answer 4

Current it shared between branches in a series circuit.

Question 5

Define current

Answer 5

Current is the rate of charge flow

Question 6

What is the equation for current?

Answer 6

Q= I x T

Question 7

Define a coulomb

Answer 7

One coulomb is that charge passing any point in a circuit when a steady current of 1 ampere flows for one second.

Question 8

What is potential difference

Answer 8

Potential difference or voltage is the amount of energy a coulomb will have. It can be increased through the use of cells, batteries etc.

Question 9

What is true about voltage in a parallel circuit?

Answer 9

In a parallel circuit the voltages across the components are the same

Question 10

What is true about voltage in a series circuit?

Answer 10

It is shared

Question 11

State ohms law

Answer 11

The current flowing through a wire is directly proportional to the voltage across it as long as temperature and other physical conditions remain constant.

Question 12

What is the equation for ohms law

Answer 12

V= I x R

Question 13

Describe the method of the investigation into ohms law experiment

Answer 13

Label all components in the circuit also label the + terminals of the battery, ammeter and voltmeter.
By changing the settings on the rheostat / variable resistor we can change the voltage across the wire and hence the current flowing across it.

(See page 19 in current electricity booklet for diagram)
Switch is included in circuit so the wire doesn’t heat up in between readings.

Question 14

What do the following prefixes mean?

Mega
Kilo
Milli
Micro

Answer 14

Mega is 1.0 x 10 to the power of 6 or 1,000,000
Kilo is 1.0 x 10 to the power of 3 or 1000
Milli is 1.0 x 10 to the power of negative 3 or 0.001
Micro is 1.0 x 10 to the power of negative 6 or 0.000 001

Question 15

How do you find the resistance in in a series or parallel circuit

Answer 15

Total voltage across both resistors ➗ current through both resistors

Question 16

How is resistance calculated in a a parallel circuit

Answer 16

If only 2 do the product divided by the sum. If more than that add reciprocals of resistors (fractions)

E.g 5 + 20 = 4

Question 17

Explain resistance in terms of electron movement

Answer 17

Resistance can be defined as opposition to the flow of current. Therefore free electrons which carry charge collide with the regularly arranged fixed atoms in the structure. These collisions provide a resistive force slowing down the current.

Question 18

Define a short circuit

Answer 18

A short circuit occurs when a wire has a lower resistance than a component so bypasses it. For example if a wire connects to points with a bulb also in between the current will travel through the wire causing the bulb to go out.

Question 19

What happens to resistance as length increases

Answer 19

It also increases. Therefore it is directly proportional.

Question 20

What happens to resistance as cross sectional area increases?

Answer 20

Resistance decreases as CSA increases therefore, they are inversely proportional.

Question 21

What happens to a brightness of a lamp as current increases

Answer 21

Brightness also increases

Question 22

What happens to temperature in the lamp filament as current increases

Answer 22

The temperature increases

Question 23

What hapless to resistance as temperature increased in the lamp filament

Answer 23

Resistance also increased

Question 24

Is voltage and current directly proportional for the lamp?

Answer 24

No both increase but it is not proportional. We can see this in the graph. This is due to the lamp being a non-ohmic component.

Question 25

Why does resistance in metal increases as temperature increases?

Answer 25

The collisions cause the atoms to vibrate more, this makes the filament glow. In turn the larger and faster vibrations cause a higher ratio in collisions therefore a higher resistance.

Question 26

What is electrical power and what is it measured in?

Answer 26

Electrical power tells us how much electrical energy is used by the appliance in one second. It’s measured in Watts

Question 27

What are equations for calculation power

Answer 27

E= P x T
P= I x V
E= ITV