8TH GRADE PRACTICE
Physics Problems: Charge and electric field, Grade 8
Electrification, atom, law of conservation of charge and field.
Here the conditions and analysis of the solution can be read without an account. In the simulator, you need to collect the same analyzes yourself: “Given,” formulas, order of steps and answer.
Problem statements
The answer options are there to check against, and the walkthrough opens under each problem.
Problem #28
Electrification, conductors and dielectricsEvaluate the statement: The process of the appearance or redistribution of electrical charge on bodies upon contact, friction or influence.
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During friction, electrons transfer between materials, so the bodies receive charges of equal magnitude and opposite signs.
Answer
Problem #29
Electrification, conductors and dielectricsEvaluate the statement: the concept “Two types of charge” means: In a conductor, charges can move throughout the body, but in a dielectric they are mainly displaced within atoms and molecules.
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The positive and negative signs are arbitrary, but they allow us to unambiguously describe the interaction and transfer of electrons.
Answer
Problem #30
ElectrificationA charged metal sphere was touched by an uncharged metal rod with an insulating handle. What will happen?
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Answer
Problem #31
Atomic structure and charge conservationEvaluate the statement: An atom consists of a positively charged nucleus and negative electrons, and a neutral atom has equal charges.
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Losing electrons forms a positive ion, gaining extra electrons forms a negative ion.
Answer
Problem #32
Atomic structure and charge conservationEvaluate the statement: the concept “Law of Conservation of Charge” means: The electric charge of a body changes in portions that are multiples in absolute value of the charge of one electron.
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During electrification, a charge is not created out of nothing: electrons move between bodies, maintaining a total charge.
Answer
Problem #33
Charge conservationTwo isolated bodies had charges +5 nC and -2 nC, then came into contact. What will be the total charge of the system?
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Answer
Problem #34
Charge interaction and electric fieldEvaluate the statement: The force of interaction between point charges is proportional to the product of the charge moduli and inversely proportional to the square of the distance.
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The direction of the force is along the line between the charges; the sign of the charges determines attraction or repulsion.
Answer
Problem #35
Charge interaction and electric fieldEvaluate the statement: The concept “Electric field” means: The accumulated charge can produce a useful attraction of particles or a dangerous spark discharge.
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The voltage shows the force per unit positive test charge, and the lines are directed from plus to minus.
Answer
Problem #36
Electric fieldCharges of 2 µC and 3 µC are in a vacuum at a distance of 0.3 m. Find the magnitude of the force, taking k = 9·10⁹ N m²/C².
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Answer
The theory behind these problems
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Formulas by topic
Look up symbols and units of measurement in the reference.