P5

Question 1

How are objects attracted to eachother after object is rubbed against one’s hair or other suface?

Answer 1

It is attracted as during the process of rubbing in gain or losses electrons, which make it positvely or negatively charged

An example of this is rubbing a baloon against your hair and then seeing how it is able to stick to walls, as it is attracted to them

Question 2

What is one model for an electric circuit?

Answer 2

+ photo

• hear the mouse represents the battery
• and the are charge - through the movement of the mouse
• the paddle wheel causes resistance, causing energy to be used in the circuit.

Question 3

What way does conventional current and which way does the electrons flow?

Answer 3

• covential current flows clockwise in a closed circuit from + to -
• electrons flow anticlockwise in a closed circuit from - to +

Question 4

What is an electric current and how is it measured?

Answer 4

• electric current is the flow of charge around a closed circuit
• greater current, more energy it can transfers
• an anmeter is used to measure the current
• slows the amount of charge going through the meter every second
• how it is connected in a circuit

Question 5

What fact remains constant about electric current in a series circuit?

Answer 5

the speed remains constant

Question 6

What are some more facts about current?

Answer 6

• the current is not used up when it flows around the circuit
• the charge is used up and transfered

Question 7

Name two types of circuits?

Answer 7

• a parallel circuit
• a series circuit

Question 8

What causes resistance?

Answer 8

• lamps
• resistors
• wire a little bit

Question 9

How do wire get hot when current flows through them?

Answer 9

• charges in the metal= electrons
• ion collide with the lattice structure of the wire
• cause energy to be transferred
• some metals have wider lattice structures which craetes less resistance for the ions or charges traveling through the wire

Question 10

How is resistance measured in a series and parallel circuit?

Answer 10

-series circuit

R1+R2= R3

-Parallel circuit

R3=1 divided by 1 over R1+ 1 over R2+1 over Rn

Question 11

What determines the size of the current?

Answer 11

• the voltage of the battery
• the resistance of the circuit compoents

Question 12

How is a voltmeter connected in a circuit, and what happens when more voltage goes through a lamp?

Answer 12

• connect across the compoent
• more voltage= brighter the lamp

Question 13

What is voltage?

Answer 13

• the voltage is the push of the current around the circuit

Question 14

What is resistance?

Answer 14

• this is a force that means more energy is required to push the current
• the resistance effects the size of the current?

Question 15

What is the formula for the resistance of a conductor?

Answer 15

resistance of a conductor= photo

Question 16

What is a fact about current and voltage?

Answer 16

• current in circuit is proportional to the voltage of the battery
• this is known as ohm’s law

resistance= the voltage divide by current

Question 17

What is a variable resistor?

Answer 17

• its resistance can be changed or varied by moving a slider or dial
• more coils of wire the current has to go through, the greater the resistance

Question 18

What bis an light dependent resistor?

Answer 18

• the more light it is exposed tp the greater the resistance

Question 19

What is a thermistor?

Answer 19

• increases resistance according to to temperature
• lower ressitance - hotter

Question 20

What is potentail difference?

Answer 20

• higher potentail energy at the begining
• lowest potential energy after the last compoent

Question 21

What does a voltmeter measure ?

Answer 21

• the potentail difference between two points e.g.

A to B

Question 22

How do you measure the power of a circuit and work done?

Answer 22

Question 23

What is the link between magnetism and electricity?

Answer 23

• when there is an electric current there is a magnetic field in the region of the wire
• winding the wire round in a coil

it strengthens the magnetic force

• each turn of the wire has its own magnetic field, which is added together

Question 24

What is an electromagnet?

Answer 24

• a wire coil around an iron core with a current running through it
• can be switched on and off

Question 25

How does an electric motor work?

Answer 25

- a permenant magnet(compass needle) experiences a force if placed in a magnetic field +photo - no forces at the two ends of the coil - yet is aforce on the two sides of the coil - forces will be at right angles to both the magnetic field and the current - one force is up - other is down - cause turning effect - coil is made with several turns of wir - stronger the turning force +photo - in a electric motor - once the coil has turned 90 degrees, the direction of the current is reversed - makes the turning continuous

Question 26

Hoe is the current of an electric motor reversed in direction?

Answer 26

- by using a split ring commutor- pair of rings and brushes - no fixed wires in motors - half the ring rubs against the brush for half a turn - changes direction of the current

Question 27

How does a generator work?

Answer 27

- this is done by moving a magnet near to a coil of wire - current only, when the magent is moving

Question 28

What is an electromagnetic induction?

Answer 28

=photo - this occurs when the magnet is removed from inside the coil - there is a smaal current in the opposite direction to the original current

Question 29

How did Faraday believe a generator to work?

Answer 29

- no movement - no voltage - magnet- moving - the magnetic field is changing - magnetic field lines arew cutting the coil - causes potential difference or voltage across the coil - in a complete circuit , voltage causes a current - magnet + coil behaves like a battery - when athe magnet is removed from the coil - the field changes - causes induced voltage in the opposite direction of the current

Question 30

What is a. c. and d. c.

Answer 30

alternating current produced by generator - current goes in two directions positive negative on a graph - changing magnetic field - direct current - from a battery and travels in one direction

Question 31

How can the size of alternating voltage produced by a generator be incraesed?

Answer 31

- stronger rotating magnet or electromegnet - rotating it faster - using a fixed coil with more turns - putting an iron core inside the fixed coil - strength of the magnetic field is in increased

Question 32

How can the size of induced voltage be increased?

Answer 32

- moving the magnet in and out more quickly - stronger magnet - using a coil with more turns

Question 33

How does a transformer work?

Answer 33

- changed the current in the primary coil induces the voltage in the secondary coil - output of the transformer depends on the number of coil of wire - more in secondary then primary - step up transformer - voltage increases - yet current in the secondary coil will be less - no greater power supplied P=IV

Question 34

What is the formula for the output of a tranformer?

Answer 34

Question 35

What was fleming left hand rule?

Answer 35