Unit 3: Electricity Flashcards
All (conceptual) notes: https://drive.google.com/drive/u/0/folders/120q0zGzo2H3hzhk2vOOarJLNkT7IigKq
PLEASE STILL GO THROUGH THE SYLLABUS STATEMENTS, ESPECIALLY THE ONE WHICH TELLS YOU WHICH CIRCUIT SYMBOLS YOU HAVE TO KNOW. ALSO LOOK AT THE PAST PAPER QUESTIONS I PUT AT THE END BECAUSE THEY SUMM UP THE TRICKY CONCEPTS YOU NEED TO KNOW ABOUT STATIC ELECTRICITY.
ALSO READ CHAPTER 17,18,19 OF THE TEXTBOOK (PHYSICS SECTION) THERES A LOT IN THERE YOU NEED TO KNOW.
State that there are positive and negative charges
State that unlike charges ___(1)____ and that like charges ___(2)____
(1) attract
(2) repel
Describe and interpret simple experiments to show the production and detection of electrostatic charges by friction
- Rubbing a balloon against a jumper
- Charged balloon running next to a tap of water
State that charging a body involves the addition or removal of _______
electrons
Distinguish between electrical conductors and insulators and give typical examples
Describe an electric field
a region in which an electric charge experiences a force
Demonstrate understanding of current, potential difference, e.m.f. and resistance
Current: A flow of charged particles
Potential difference: The amount of energy transferred by each unit of charge passing between two points.
e.m.f: The phenomena that allows charge to flow. it is the energy per unit charge.
Resistance: A measure of how much opposition there is to the flow of current. measured in ohms.
Remember: IT IS ALWAYS AND ONLY THE _____(?)_______ CHARGES (ELECTRONS) THAT ARE TRANSFERRED. THE POSITIVE CHARGES ARE INSIDE THE NUCLEUS OF THE ATOMS AND DO NOT MOVE.
NEGATIVE
State that current is related to the flow of charge
Remember that the flow of charge could also include the flow of cations/anions, it is only/mainly in metals where it is due to the flow of electrons
State that current in metals is due to a flow of _________
electrons
State that the potential difference (p.d.) across a circuit component is measured in volts
Use and describe the use of an ammeter and a voltmeter, both analogue and digital
State that the electromotive force (e.m.f) of an electrical source of energy is measured in volts
Show understanding that a current is a rate of flow of charge and recall and use the equation
interlinking current, time, and charge
I = Q / t
Define EMF
energy supplied by a source in driving charge around a complete circuit
State that resistance = (what is the equation for resistance?) and understand qualitatively how changes in p.d. or resistance affect current
p.d. / current
Think of it like this:
current x resistance = potential difference
now just rearrange that equation
Current is directly proportional to electric potential difference and inversely proportional to resistance.
Recall and use the equation R = V / I
Sketch and explain the current-voltage characteristic of an ohmic resistor and a filament lamp
Recall and use quantitatively the proportionality between resistance and length, and the inverse proportionality between resistance and cross- sectional area of a wire
Draw and interpret circuit diagrams containing sources, switches, resistors (fixed and variable), lamps, ammeters, voltmeters and fuses (Symbols for other common circuit components will be provided in questions.)
fixed resistors = resistance doesn’t changed, variable resistor = resistance changes
Cell symbol - the logner line = positive side, shorter line = negative end
Understand that the current at every point in a series circuit is the same
Calculate the combined resistance of two or more resistors in series
State that, for a parallel circuit, the current from the source is larger than the current in each branch
because total current = sum of the current in each branch.
Lets imagine this - a river splitting its course into two paths. Lets say that one of the paths has too many rocks, while the other path is a plain piece of land. Where does most of the water flow? Its the plain path isn’t it? It offers less resistance and hence favours the flow of water.
Yes. The same applies to current flow in circuits as well. Electric current is nothing but flow of electrons. And different paths in a circuit may have different resistances. So, currents in parallel branches may be different.