P4 - Electric Circuits Flashcards
What is an electric field?
A charged object (X) creates an electric field around iteself, which causes a non-contact force on any other charged object in the field
What are electrons?
Tiny negatively charged particles that move around the nucleus of an atom
What is an ion?
A charged atom or molecule
What is a line of force in an electric field?
Line along which free positive charge moves along in an electric field
What are neutrons?
Uncharged particles of the same mass as protons. The nucleus of an atom contains both protons and neutrons
What is potential difference?
A measure of the work done or energy transferred to a device by each coulomb of charge that passes through it. The unit of potential difference is the volt (V)
What are protons?
positively charged particles with an equal and opposite charge to that of an electron
What is the equation for resistance?
Resistance = potential difference / current
What is the unit of resistance?
Ohms (Ω)
What is static electricity?
Electric charge stored on insulated objects
How can you charge an object?
Charge by friction, by rubbing 2 insulating materials together electrons are transferred from 1 material to the other. Materials that gain electrons become negatively charged, materials that lose electrons are positively charged
What type of force is electrostatic force?
Non-contact
What happens if 2 like charges become close to each other?
They repel each other
What happens if 2 opposite charges come near each other?
They attract
How do charged objects exert forces on each other?
A charged object creates an electric field around itself. The field is strongest closest to the object
What happens to the strength of the electric field as distance from the charged point increases?
Decreases
Draw the diagram for a positive and negative electric field
Describe how a balloon can stick to a wall due to electrostatic attraction
A balloon is normally neutrally charged, however when rubbed against another insulator (such as a dry cloth) it will become positively or negatively charged due to gaining or losing electrons. As the balloon is now charged, the opposite charge is induced on the wall due to electrons being attracted or repelled. The wall is then attracted as opposite charges attract. This electrostatic attraction causes the balloon to stick to the wall
Describe how a charged object can attract a neutral object
A charged object can attract a neutral object as it will induce a charge on the neutral object due to electrons in the neutral object being attracted or repelled
Why can conductors not become charged by friction?
Conductors cannot hold the charge, as the electrons can move through them
Why can an insulator become charged?
Insulators prevent the electrons from moving and the charge remains static
What are the advantages of using static electricity to help coat a car with paint?
- There is less paint wasted due to the attraction of the oppositely charged paint and car body.
- The application of paint is more even over the entire car body as the entire car can be coated, even when not in the direct line of paint
Describe how the strength of the electric field varies with distance in the electric field between oppositely charged parallel plates
The strength of the electric field is constant through the separation between the plates, this is because as you travel further from the positive plate, despite the strength of the positive electric field decreasing as you are further from it, the strength of the negative electric field increases as you are closer to it
Describe the motion of a proton when placed close to a positive point charge
The positively charged proton will accelerate away from the positive charge due to the repulsion of the positive proton and positive point charge. However, the protons acceleration will decrease with distance from the positive point charge, this is because the electric field strength decreases with distance from the positive point charge
Describe the motion of a proton when placed close to the positive plate in the uniform field
The proton will accelerate with a constant acceleration from the positively charged plate to the negatively charged plate
What is an electric current?
The flow of charge
What is the charge in a circuit carried by?
electrons
What is the unit of current?
Amperes (Amps)
What does 1 amp represent?
rate of flow of 1 coulomb per second
What is the equation for current?
Current (I) = Charge (Q) / time (t)
What is the equation for potential difference?
Potential difference (V) = Energy (E) / Charge (Q)
What is resistance?
Electrical resistance is the opposition to the flow of charge. It is measured in Ohms
What is Ohms law?
The current through a resistor at a constant temperature is directly proportional to the potential difference across the resistor
What is used to measure current?
Ammeter
What is used to measure potential difference?
Voltmeter
What happens to the resistance of a wire if temperature is increased?
Heating the wire causes atoms to vibrate more, which in turn makes it more difficult for the electrons to flow, increasing resistance
What charge does an electron carry?
Negative charge
What is the unit of charge?
Coulombs (C)
What happens to the current if you increase the resistance?
The greater the resistance across a component, the smaller the current that flows
What causes sparks?
As static electric charge builds up on an object, a strong electric field between the charged object and the earth (or earthed object) is made. The strong electric field causes the air to become ionised as electrons are removed from the air particles. This causes the air to become conductive causing the current to flow through it. This movement of electrons is the spark you see
What 2 forms of energy are emitted from a light bulb?
Useful: Visible Light Radiation
Wasted: Thermal Energy
Explain what causes electrons to move from an area with a build up of electrons to an area without a build up of electrons
Due to a build of electrons and charge, there is a potential difference between the area with a build up of electrons and the area without. This causes some of the electrons to transfer to the area without a build up of electrons
Explain how a negatively charged student receives an electric shock when they touch a metal tap:
There is a potential difference between the student and the tap, this causes the electrons to transfer from the student to the tap. This earths the charge causing an electric shock
What is earthing an object?
the process of removing the excess charge on an object by means of the transfer of electrons between it and another object, causing the object to become neutral
