Science 9 - Physics Unit Test

Question 1

Difference between static and current electricity

Answer 1

Static = electrons not moving (charge is static)
Current = electrons moving freely through conductor

Question 2

How is charge produced?

Answer 2

Charge is produced by the transfer of electrons. (gain or loss)

Question 3

attraction & repulsion

Answer 3

same charges repel
opposite charges attract
neutral and charged objects attract
two neutrals = no effect

Question 4

how to determine charge of an object?

Answer 4

test against an object with a known charge, ie; a vinyl strip or a acetate rod. a vinyl strip is always negative so if something attracted it, you would know the object is either neutral or positive. two deduce which one it is, you would then charge it against the acetate rod, and if it attracted to the acetate as well, you would know it is neutral. if it repelled, you would know it was positive.

Question 5

charging by conduction

Answer 5

charged object makes contact with uncharged object (electrons flow from one object to another)

Question 6

charging by induction

Answer 6

no contact made between two objects

Question 7

difference between insulators and conductors

Answer 7

in an insulator the charge is held in one place (the electrons are static) in a conductor the charge moves freely throughout it

Question 8

uses for static charge

Answer 8

plastic wrap, electrostatic spray painting, making balloons, photocopiers

Question 9

what is an electrochemical cell made of? how does it work?

Answer 9

made of electrodes of two different metals and a conducting solution. metals have different abilities to gain or lose electrons, metals chosen have opposite abilities. lost electrons travel through wires of the circuit. ions travel through solution to keep system neutral.

Question 10

relationship between electric potential energy and electric potential difference/voltage

Answer 10

unlike charges moved farther apart, they gain electric potential energy. electric potential difference/voltage is the change in potential energy per coulomb of charge.

Question 11

examples of electrical energy sources

Answer 11

simple generator, complex generator, piezo-electric crystals, electrochemical cells, thermo-couple, solar cells

chemical, thermal, kinetic, nuclear, solar, rotational

Question 12

electron and conventional current flow

Answer 12

electron flow = negative to positive
conventional current - positive to negative
(we now know conventional current flow is false because protons cannot move, only electrons can)

Question 13

components of a circuit

Answer 13

dry cell, battery, switch, ammeter, voltmeter, light bulb, resistor, fuse, motor

Question 14

current electricity

Answer 14

rate at which charge passes through a point in a circuit.
measured by an ammeter
measured in amps

Question 15

difference between power and energy

Answer 15

electric power is rate at which electric potential energy is transformed.

Question 16

series circuit

Answer 16

• resistance total = r1 + r2
• current same everywhere
• voltage spread between all loads and add up to total V

Question 17

parallel circuit

Answer 17

• resistance total = 1/rT = 1/r1 + 1/r2
• current different in different branches (branches add up to total main branch)
• voltage same everywhere

Question 18

static problems/dangers + solutions

Answer 18

• clothes out of dryer (use dryer sheets/fabric softener)
• dry fly-away hair (use hair product or wet hair)
• doorknobs (ground yourself, remove carpeting)
• lightning (use lightning rod)

for all situations except lightning, an alternative is to humidify the house