Electricity

Question 1

What is the pnuemonic for the 5 key equation triangles

Answer 1

Can Jay Very Well Afford Chocolate Since Jay Went Away Often

Write in a Zigzag so that you can draw the triangles accordingly

   J           W        C          J C           V          A           S          W 
    A          O

Question 2

When an object gains or loses electrons what do the lines of forces look like and what do the lines represent (5)

Answer 2

When an object gains electrons, it creates an electrical field around itself

Drawing lines of forces:

the lines need to be coming straight out of the object, not at an angle
the lines need arrows
when the object is positively charged, the arrows face out of the object
when the object is negatively charged, the arrows face in to the object
the strength of the field is represented by how long the arrows are

Question 3

which object gains and loses electrons in these 2 scenarios
Polythene rod + dry cloth –>

Perspex rod + dry cloth –>

Answer 3

Polythene rod + dry cloth –> rod gains electrons

Perspex rod + dry cloth –> cloth gain electrons

Question 4

what is the difference between cell and battery

Answer 4

the difference between a cell is that a batter is made up of more than one cell so a cell looks like -| - whereas a battery is -| \ | \ | -

Question 5

does a circuit work with an open switch or a closed switch and why (2)

Answer 5

closed switch as the electrons can flow through whereas with open switch there is a break in the circuit so the electrons cannot flow through

Question 6

what does a diode do

Answer 6

allows current in one direction only

Question 7

draw the circuit symbol for a diode

Answer 7

search up and see if correct

Question 8

For a light emitting diode, do the 3 arrows point in or out

Answer 8

out

Question 9

draw the circuit symbol for a heater

Answer 9

search up and see if correct

Question 10

draw the circuit symbol for a LED

Answer 10

search up and see if correct

Question 11

draw the circuit symbol for a Volt meter

Answer 11

search up and see if correct

Question 12

draw the circuit symbol for a Amp meter

Answer 12

search up and see if correct

Question 13

draw the circuit symbol for a fixed resister

Answer 13

search up and see if correct

Question 14

draw the circuit symbol for a variable resister

Answer 14

search up and see if correct

Question 15

draw the circuit symbol for a fuse

Answer 15

search up and see if correct

Question 16

what is the symbol for current

Answer 16

I

Question 17

what is the unit for current

Answer 17

A (Amps)

Question 18

what is the unit for charge

Answer 18

C (Coulombs)

Question 19

what is watts the unit of

Answer 19

P (Power)

Question 20

What is the relation between a, b and c in a physics equations, for example Q=IR

Answer 20

When your equation is a=bxc, the relationships are as follows:

a is directly proportional to b
a is directly proportional c
b is indirectly proportional to c

Question 21

What is voltage

Answer 21

In a circuit, think of the voltage as the driving force - the voltage is the amount of energy being given to each electron, which then determines how fast the electron can move (the current - the speed of electron flow )

Question 22

what is current

Answer 22

current = the rate of flow of charge

Question 23

What are electrons flowing through in a wire

Answer 23

in the copper coil, electrons are not running a marathon, they are running on an obstacle course filled with positive metal ions

Question 24

explain resistance in terms of electrons running

Answer 24

As these electrons run around, they bump into these ions - the faster the electrons are running (higher current), the more they are bumping into each other and positive ions (higher resistance)higher resistance means more heat is generated

Question 25

what is the formula for resistance in a series ciruit

Answer 25

Total resistance = R1 + R2

Question 26

what is the formula for resistance in a parrelel circuit

Answer 26

1/total resistance = 1/R1 + 1/R2

Question 27

what is ohms law

Answer 27

Ohm’s Law = In a conductor, the current is always directly proportional to the potential difference aross it, as long as the temperature is constant

Question 28

list some examples of an ohmic conducter

Answer 28

A wire is an ohmic conductor, as well as a filament light bulb

Question 29

what happens to the a current potential difference graph when the resistance increases

Answer 29

In a current, pd graph, as the resistance increases, the gradient decreases

Question 30

draw a current pd graph for an ohmic conducter ( wire/ resister)

Answer 30

Look at page 78 figure 8.6

Question 31

draw a current pd graph for a filament lightbulb

Answer 31

Look at page 78 figure 8.7

Question 32

draw a current pd graph for a diode

Answer 32

Look at page 78 figure 8.8

Question 33

what is a thermister and how does it work

Answer 33

Thermistor = a temperature dependent resistor If temperature increases, its resistance decreases, and if temperature decreases, the resistance increases

Question 34

what is a LDR stand for and how does it work

Answer 34

LDR = light dependent resistor If light intensity increases, resistance decreases, and if light intensity decreases, resistance increases.

Question 35

what are thermistors used in

Answer 35

Thermistors are used in fire alarms, freezers and computers

Question 36

what are LDRs used in

Answer 36

LDR are used automatic light controls and burglar alarms

Question 37

what are diodes used in

Answer 37

Diodes are used in light emitting diodes. They are also used to convert alternating currents to direct currents, in rectifier circuits

Question 38

which one is positive and which one is negative when you rub a plastic ruler on some pieces of paper

Answer 38

ruler postive and the paper is negative