GED Science
Waves, Heat & Electricity
Waves carry energy without carrying stuff — sound through air, light through space. Heat always flows from hot to cold, by three routes. Electricity is charge moving around a loop, governed by one small formula. Three small kingdoms, each with a couple of rules.
The words first
- wavelength / frequency
- distance between crests / crests passing per second — long wavelength means low frequency
- amplitude
- wave height = its energy (louder sound, brighter light)
- conduction / convection / radiation
- heat by touch / by rising-sinking fluid / by rays through space
- V = I × R
- voltage = current × resistance (Ohm's law)
The method
WAVES
~~~~~~~~ long wavelength = low frequency = low pitch
^v^v^v^v short wavelength = high frequency = high pitch
taller wave = more energy (volume, brightness)
sound needs a medium; light does not (space is silent)
HEAT'S THREE ROUTES (always hot → cold)
conduction spoon handle warming in soup (touch)
convection hot air rising, cool sinking (fluids circulate)
radiation sun warming your face (rays, no contact)
ELECTRICITY — Ohm's triangle
V
───── I = V ÷ R R = V ÷ I V = I × R
I │ R
series circuit: one path — one bulb dies, all die
parallel: separate branches — one dies, rest stay lit (your house)
Worked all the way through
The problem
A 120-volt outlet powers a lamp with 60 ohms of resistance. How much current flows through it?
- Step 1 — Cover the wanted letter on the triangle.Want current: I = V ÷ R.
- Step 2 — Substitute.I = 120 ÷ 60.
- Step 3 — Divide and attach units.I = 2 amps.
- Step 4 — Feel the relationship.More resistance would mean less current from the same outlet — R sits under the divide.
On the board
I = V ÷ R
cover the I
I = 120 ÷ 60
I = 2 amps
double the R → half the I
the tradeoff
Answer
2 amps
A second one, in a different form
One string of old holiday lights goes fully dark when a single bulb burns out; the lights in your house don't. Why?
old string: series — one path
a break stops everything
house wiring: parallel — branches
one branch breaks, others still loop
series vs parallel
the whole answer
Answer
The string is wired in series (one path); the house is parallel (independent branches)
The usual mistake
Assuming metal is colder than wood at the same temperature. It just conducts heat away faster.
Check yourself
Match the units to the kingdom before computing — volts, amps, and ohms go in Ohm's triangle; wavelength and frequency trade off inside waves; and heat questions are answered by naming the route: touch, circulation, or rays.
Practice it
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