Electricity, Magnetism & Light — Problem set, Grade 6
How do fields, circuit paths, and light models explain observable changes? Which modeled circuit keeps lamp B available when lamp A is switched off, and what does the evidence not show?
Review the key ideas
Electric Charge, Attraction & Materials
There are two kinds of electric charge, and rubbing two materials together does not create either one: it moves electrons from one surface to the other, leaving one short and one with a surplus. A charged object can attract something uncharged, and the reason is worth understanding properly.
Simple Circuits: Paths, Switches & Energy
Charge travels round a complete loop and is not used up anywhere in it; what gets used up is energy. Getting that distinction right is what makes series and parallel circuits predictable instead of mysterious.
Magnetic Forces, Fields & Distance
Only a handful of materials are magnetic, and the common belief that all metals are is wrong and easy to disprove. A magnet acts through a field whose strength falls away extremely quickly with distance, which is why magnets must almost touch to be useful.
Light, Shadows & Reflection
Light travels in straight lines at about 300,000 km/s, and almost everything you see is light that left a source, bounced off an object and entered your eye. Shadows, mirrors and the simple fact that you can see a wall from any angle all follow from those two statements.
Refraction, Color & Transparent Materials
Light slows down when it enters glass or water, and because it slows it changes direction at the boundary. That single fact explains the broken-looking straw, why a pool is deeper than it looks, why a prism makes a spectrum and why a rainbow exists.
Problem 1
Answer and explanation
A has ten positive and eight negative units, a net positive two. B has ten positive and twelve negative, a net negative two. The combined twenty positive and twenty negative units remain; charge is transferred, not created. These are model units, not measured coulombs or a rule for every rubbed material.
Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.
Problem 2
Answer and explanation
No. Polarization can shift the interaction without requiring an opposite total net charge. Explain the modeled distribution rather than infer net charge from attraction alone.
Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.
Problem 3
Answer and explanation
The parallel branch design provides the modeled independent control: opening A does not interrupt B’s complete path. The common switch can still stop both. The records do not establish equal brightness, battery lifetime, or a safe real construction; those require a rated design and further evidence.
Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.
Problem 4
Answer and explanation
Inspect an approved kit’s contacts and source condition under adult guidance, or evaluate those possibilities in the supplied record. A complete drawing does not establish that every actual component functions.
Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.
Problem 5
Answer and explanation
The recorded holding count decreases as gap increases under this method. At 2 cm the mean is 5 clips and the range 4–6. Clip count is a practical proxy, not force in newtons, and these three distances do not establish an exact mathematical law or prove the field stops beyond 3 cm.
Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.
Problem 6
Answer and explanation
No. Metals differ in magnetic response, and the method has limits. Attraction is not a universal test for all metal identity.
Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.
Problem 7
Answer and explanation
The correct reflected angle is 40° from the normal and 50° from the surface. Drawing 40° from the surface makes it 50° from the normal, so the mismatch comes from the reference line. These are ideal ray-model angles, not a record of an actual mirror trial.
Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.
Problem 8
Answer and explanation
No. Source–object–screen distances and source size affect shadow geometry. Check those conditions before claiming a change in the object.
Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.
Problem 9
Answer and explanation
The ray bends toward the normal because 22° is less than 35° in this air-to-water model. The card appears dark because the red-only source supplies no blue for it to reflect. These diagrams omit detailed wavelength response, intensity, and actual material variation; they are not universal measurements of every card or liquid.
Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.
Problem 10
Answer and explanation
A ray traveling directly along the normal can change speed without changing direction. Refraction’s speed change and oblique bending must be distinguished.
Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.