P2.3 (Currents)

Question 1

What is static electricity?

Answer 1

Static electricity is a stationary electrical charge

Question 2

What are the rules of attraction?

Answer 2

If the charges are the same, they REPEL
If the charges are opposite they ATTRACT
If one is charged and one is not they ATTRACT

Question 3

If a substance loses electrons, what is it’s charge?

Answer 3

POSITIVE

Question 4

Does a substance gain or lose electrons in order to become negatively charged?

Answer 4

GAIN

Question 5

How do you work out power?

Answer 5

Power = voltage x current

Question 6

How do you work out voltage?

Answer 6

Voltage = power / current

Question 7

What is current measured in?
What is voltage (potential difference) measured in?
What is power measured in?

Answer 7

A (amps)
V (volts)
W (watts)

Question 8

What is the power of a 5 A 1.5 V lamp?

Answer 8

5 x 1.5 = 7.5W

Question 9

What is the purpose of fuses?

Answer 9

The fuse keeps the circuit safe as it burns out when the current increases past the current the fuse can handle.

It does this by being a thinner wire than the rest of the circuit and so when the current increases, the resistance in the thin wire becomes too much and the wire burns out.

Question 10

Is the current equal in all parts of the circuit in a series or parallel circuit?

Answer 10

A SERIES CIRCUIT

Question 11

How is the current distributed in a parallel circuit?

Answer 11

It splits between branches

Question 12

What’s Kirchoff’s second law?

Answer 12

Sum of PD’s in a cell = sum of PD’s in each branch

Question 13

How is the potential difference distributed in parallel and series circuits?

Answer 13

In a parallel circuit the potential difference is the same in every component
In a series circuit the potential difference splits between components.

Question 14

SERIES SYMBOLS

Answer 14

LOOK IN BOOK

Question 15

What is the equation for resistance distribution in a series circuit?

Answer 15

Rt = R1 + R2

in book diagram

Question 16

What is the equation for resistance distribution in a parallel circuit?

Answer 16

1/Rt = 1/R1 + 1/R2

Rt is less than either resistance

Question 17

Why does static electricity only work with insulators not conductors?

Answer 17

In conductors, the electrons are able to flow away instead of staying static

Question 18

What is potential difference?

Answer 18

The energy given to/by electrons

Question 19

What would the resistance in a circuit do as the temperature increased?

Answer 19

decrease

Question 20

In an LDR, does the resistance rise or fall with the intensity of the light?

Answer 20

FALLS

Question 21

How do you work out charge?

Answer 21

Charge = current x time

C = A x S

Question 22

How do you work out work done?

Answer 22

Work done = potential difference x charge

Question 23

Does the resistance increase or decrease through a thin wire and why?

Answer 23

The resistance will increase as there is less space for the electrons to flow so they bump into each other and lose energy causing the wire to heat up.

Question 24

What is resistance?

Answer 24

A measure of how much obstruction there is to an electrical flow.

Question 25

If you get a shock after touching a metal object, are you a conductor or insulator?

Answer 25

Insulator

Question 26

What is the relationship between current and voltage?

Answer 26

Current and voltage are always directly proportional to each other at constant temperature

Question 27

What does an IV graph show?

Answer 27

For a particular component, an I-V graph shows what current will flow across the component when a potential difference is applied

Question 28

What gives wires resistance?

Answer 28

Electrons moving through the wire collide with fixed ions and lose energy, in thinner wires collision is more likely

Question 29

Two resisters of 100 Ω and 50 Ω are connected in series. The voltage drop across the two resisters is 15V. What is the current running through the circuit?

Answer 29

0.1 A 100 + 50 = 150 15 /150 = 0.1