Electricity

Question 1

What is electric current ?

Answer 1

The amount of charge flowing in the circuit per second / the rate of flow of charge

Question 2

What is the current measured using ?

Answer 2

An ammeter , a device with zero resistance connected in series to allow all the charge to flow through accurately reading the current

Question 3

What is electric charge ?

Answer 3

The amount of charge that passes a fixed point in one second with a current of 1 ampere.

Question 4

What is the charge of one electron ?

Answer 4

• 1.6 * 10 ^-19

Question 5

What is potential difference ?

Answer 5

Potential difference is the amount of work done or energy transferred per coulomb of charge that passes between two points

Question 6

How Is the potential difference measured ?

Answer 6

A voltmeter in parallel across the component in a circuit with almost infinite resistance to have 0 current flowing through it to accurately measure the work done

Question 7

What is resistance ?

Answer 7

The ratio of potential difference to current and tells us how easy or difficult it is for current to flow through it , measured in ohms

Question 8

What does ohms law state ?

Answer 8

The potential difference is directly proportional to the current , provided that the temperature is constant

Question 9

What is an ohmic conductor ?

Answer 9

A conductor that follows ohms law and has a constant resistor

Question 10

What are the factors that the resistive depends on ?

Answer 10

The length - the greater the length the higher the resistance
Area of cross section - the greater the area, the lower the resistance
Material - constant for restivity

Question 11

What is a ntc thermistor?

Answer 11

A negative temperature coefficient thermistor is a resistor where the resistance decreases as the temperature increases. They absorb the energy and release free electrons increasing the current flow.

Question 12

What is an ldr ?

Answer 12

A light dependent resistor is a resistor where the resistance decreases as the light intensity increases . They are used as light sensors to switch on devices such as street lamps when it gets dark

Question 13

What is superconductivity ?

Answer 13

It is a property of certain materials which have zero resistivity at and below a critical temperature which depends on the material.

Question 14

What is meant by critical temperature?

Answer 14

The temperature at which a material becomes a superconductor

Question 15

What are benefits of using superconductors -

Answer 15

• as there is no resistance there is no energy and power loss
• when the current is high due to low resistance they generate strong magnetic fields

Question 16

Uses of superconductors:

Answer 16

• mei scanners , transformers and generators, motors , particle accelerators

Question 17

If resistors are places in series what is the total resistance ?

Answer 17

The sun of each resistance so he total resistance would be greater than the each individual resistance

Question 18

What is the total resistance of resistors in parallel ?

Answer 18

1/rt = 1/r1 + 1/r2 … so the total resistance would be smaller than each individual resistance

Question 19

When cells are placed in series what would the total potential difference be ?

Answer 19

The sum of the potential differences

Question 20

When cells are placed in parallel , the total potential difference supplied is ?

Answer 20

The total potential difference supplied is equal to the potential difference of one of the cells

Question 21

What does Kirchhoff first law state ?

Answer 21

The total current entering a junction is equal to the current leaving a junction , due to the conservation of charge

Question 22

What does Kirchoffs second law state ?

Answer 22

In any complete loop within a circuit , the total voltage supplied must be equal to the sum of potential differences across all the components, due to the conservation of energy

Question 23

Define electrical power :

Answer 23

The rate at which work is done or the rate at which energy is transferred