Electric charge
20 flashcards to master Electric charge
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State the two types of electric charge that exist. Explain how these charges interact with each other.
Answer:
There are two types of electric charge: positive and negative.
* Like charges repel: Positive-positive and negative-negative charges repel each other.
* Opposite charges attract: Positive-negative charges attract each other.
A neutral balloon is rubbed against a wool sweater. After rubbing, the balloon has an overall negative charge. State what this indicates about the charges transferred between the balloon and the sweater.
Answer:
The balloon gaining a negative charge indicates that negatively charged particles (electrons) have been transferred from the wool sweater to the balloon. The sweater would then be positively charged.
Explain how two positively charged objects interact with each other and why this interaction occurs.
Positively charged objects repel each other. This is because objects with the same type of charge exert a repulsive electrostatic force on each other.
State what will happen when a negatively charged balloon is brought near a positively charged wall.
The negatively charged balloon will be attracted to the positively charged wall. Unlike charges attract each other.
Describe a simple experiment to demonstrate the production of electrostatic charge by friction using a plastic rod and a cloth. Explain how you would detect the presence of this charge.
1. Rub the plastic rod vigorously with the cloth. (1 mark)
2. Bring the rod near small pieces of paper. If the paper is attracted to the rod, this indicates the presence of an electrostatic charge. (1 mark) Friction transfers electrons, creating a charge imbalance on the rod.
State two observations that would lead you to conclude that an object possesses an electrostatic charge after being rubbed with a cloth.
1. Attraction to small, lightweight objects (
Explain why, when a plastic rod is rubbed with a wool cloth, the rod becomes negatively charged and the cloth becomes positively charged.
Rubbing transfers electrons. Electrons, having a negative charge, move from the wool cloth to the plastic rod. This makes the rod negatively charged (more electrons) and the wool cloth positively charged (fewer electrons). Only electrons are transferred, not positive charges.
When a student rubs a glass rod with a silk cloth, the glass rod becomes positively charged. Describe what happens during this process at the atomic level. Reference electron transfer in your answer.
Electrons are transferred from the glass rod to the silk cloth. The glass rod loses negatively charged electrons, resulting in a net positive charge. The silk gains these electrons, becoming negatively charged. Only negatively charged electrons are transferred; protons do not move.
Describe an experiment using a battery, bulb, wires, and the material under test to distinguish between electrical conductors and insulators. Explain how the results identify each type of material.
Experiment: Connect the battery, bulb, wires, and the material under test in a series circuit.
Observation: If the bulb lights, the material is a conductor. If the bulb does not light, the material is an insulator.
Explanation: Conductors allow electric current to flow, completing the circuit and lighting the bulb. Insulators resist the flow of current, preventing the bulb from lighting.
A student tests a piece of copper wire and a plastic ruler using a circuit. State what they would observe in each case and what this indicates about their properties.
Copper Wire: The bulb will light up. This indicates that copper wire is a good conductor of electricity.
Plastic Ruler: The bulb will not light up. This indicates that the plastic ruler is an insulator and does not conduct electricity.
Explain, using a simple electron model, the difference between electrical conductors and insulators.
Conductors have many free electrons that can move easily through the material, carrying charge. Insulators have very few free electrons; their electrons are tightly bound to atoms and cannot move easily. This prevents charge flow.
State two typical examples of electrical conductors and two typical examples of electrical insulators.
Conductors: Copper, Aluminium. Insulators: Rubber, Plastic. Conductors allow electrons to flow. Insulators impede electron flow.
State the unit used to measure electric charge. Explain what this unit is named after and give its symbol.
Answer:
The unit used to measure electric charge is the coulomb.
It is named after Charles-Augustin de Coulomb, a French physicist. (1 mark)
Its symbol is C. (1 mark)
A lightning bolt transfers a substantial amount of electric charge. Explain what property of electrons and protons makes the concept of electric charge necessary to describe electrical phenomena.
Answer:
Electrons and protons possess the fundamental property of charge. (1 mark)
This intrinsic charge enables them to exert electromagnetic forces on each other, attracting if opposite (electron and proton) and repelling if alike (electron and electron, proton and proton), leading to electrical phenomena. (1 mark)
Explain what is meant by an electric field. Include a description of how a charged particle interacts with it.
An electric field is a region of space where an electric charge experiences a force. A charged particle placed in the field will experience a force; the direction of the force depends on the sign of the charge (positive or negative) and the direction of the electric field.
Describe the electric field around a single positively charged sphere. Include how another positive test charge would react if placed within the field.
The electric field around a positively charged sphere is radial, directed outwards. A positive test charge placed in this field would experience a repulsive force, moving away from the sphere along a radial line.
A stationary positive test charge is placed in an electric field. Explain what determines the direction of the electric field at the location of the test charge.
The direction of the electric field at that point is the same as the direction of the electric force acting on the positive test charge. The electric field lines point in the direction a positive charge would move if placed in the field.
A positive charge experiences a force of 7.1 N to the right when placed at point P in an electric field. State the direction of the electric field at point P.
The direction of the electric field at point P is to the right. This is because the electric field direction is defined as the direction of the force on a positive charge.
Describe the electric field pattern around a small, negatively charged conducting sphere. Include the direction of the electric field lines.
The electric field lines are radial, pointing inwards towards the centre of the sphere. The field strength decreases with increasing distance from the sphere. Explanation: Electric field lines always point from positive to negative and are perpendicular to the surface of the conductor.
Two oppositely charged parallel conducting plates are separated by a small distance. State how the electric field lines are arranged between the plates, neglecting end effects. Also, state the direction of the field.
The electric field lines are parallel and equally spaced, indicating a uniform field strength. The electric field lines point from the positive plate to the negative plate. Explanation: Uniform field is created between plates; the direction of electric field is the direction a positive charge would be pushed.
Key Questions: Electric charge
State the unit used to measure electric charge. Explain what this unit is named after and give its symbol.
Answer:
The unit used to measure electric charge is the coulomb.
It is named after Charles-Augustin de Coulomb, a French physicist. (1 mark)
Its symbol is C. (1 mark)
About Electric charge (4.2.1)
These 20 flashcards cover everything you need to know about Electric charge for your Cambridge IGCSE Physics (0625) exam. Each card is designed based on the official syllabus requirements.
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- 1 Definitions - Key terms and their precise meanings that examiners expect
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After mastering Electric charge, explore these related topics:
- 4.1 Simple phenomena of magnetism - 22 flashcards
- 4.2.2 Electric current - 12 flashcards
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