P5 Flashcards

Questão	Responda
What is an atom made up of?	An atom is made up of charges particles, it has a positive nucleus, and negative electrons orbiting it. The nucleus is made up of neutral neutrons and positive protons.
What is the name given to the force between charged objects. Give an example of this.	There are electrostatic forces between charged objects, e.g hair stands up when it is attracted to a charged comb.
Explain why rubbing two objects together can make them charged.	Electrons are transferred between one object and another.
Why are metals good electrical conductors?	Metals have free electrons, meaning that there are lots of charges free to move.
Why are plastics better electrical insulators than conductors?	Plastics are electrical insulators, as they have very few free electrons - so few charges able to move.
What is the flow of charge in a circuit also known as?	It is known as the electric current.
When a bulb is lite, there is an electric current. What is the role of the moving electrons in the circuit?	The moving electrons, or electric current, transfer energy to light the bulb. As this happens, electrical energy is transferred to light (and heat) energy.
What is the electric current also known as?	It is the rate of flow of charge, or the charge flowing per second.
The __ energy the charged particles receive from the power supply, the ____ the current.	The MORE energy the charged particles receive from the power supply, the GREATER the current.
What is an ammeter?	An ammeter is used to measure current. It is connected in series.
What is a voltmeter?	A voltmeter is used to measure voltage, and is connected in parallel across a component in a circuit.
If there is a large voltage of a battery in a circuit, the bigger the ___?	Current.
What is the formula used to find the Power?	Power (W) = voltage (V) x current (A)
What is the potential difference?	The potential difference is the difference in energy per unit charge. It is the scientific term for voltage.
What lowers a current in a circuit?	•Higher resistance •Lower voltage
What is resistance a measure of?	Resistance is a measure of how much a conductor opposes the current. The resistance is given in ohms (Ω)
Which specific type of wire has very low resistance?	Copper wires have such low resistance that we can ignore it.
What is a variable resistor?	A variable resistor is a device that allows you to control the current by changing the amount of resistance wire in a circuit.
What is the formula used to find resistance?	Resistance (Ω) = voltage (V) / Current (A)
If components connected in a series are in a line, is the current the same through all the components, or different for each one?	The current is the same through all the components connected in series.
Explain why resistors get hotter when an electric current is flowing through them.	•The electrons collide with the positive metal ions, causing the ions to vibrate more, resulting in an increase in temperature.
What is a thermistor?	A thermistor is a semiconductor, with its resistance changing as temperature changes.
What is a light dependent resistor?	It is a semiconductor which changes in resistance as the amount of light falling on it changes. In bright light, the resistance will be low.
Why does resistance increase with increasing temperature?	The increase in temperature causes the metal ions to vibrate more erratically at faster speeds, increasing the chance that an electron will collide with it, therefore there is a higher resistance as the current is moving slower through the circuit.
Is more work done by a charge with a higher or lower resistance?	More work is done by the charge when there is a larger resistance.
What is a magnetic field?	A magnetic field is a space around a magnet in which a magnetic force acts.
When is the magnetic field at its strongest?	When the field lines are closest together.
How is a voltage induced?	A voltage is induced when a magnet is moved near a piece of wire - visa versa. If the piece of wire is part of a circuit, a current will flow.
How can you increase the voltage induced?	•Increase the rotations of the wire in the coil / increase the speed of the motion. •Use a stronger magnet. •Use an iron core inside the coil.
When is a continuous supply of electricity produced?	When there is a continuous relative motion between a magnet and a coil of wire.
What is electromagnetic induction?	It is when the coils of wire continuously 'cut' the magnetic field lines so a voltage is induced.
As a coil rotates, it cuts the lines of magnetic fields at different rates. What are these different rates?	At right angles to the field lines, it cuts no field lines, so a voltage is not induced. •When parallel to the field lines, the rate at which it cuts the field lines is at its maximum, so the induced voltage is at its highest. •As the coil rotates, it cuts fields in a different direction, so the direction of the voltage alternates.
What is a direct current?	A direct current always flows in the same direction, like a battery.
What is an alternating current?	An alternating current (a.c) changes at regular intervals. In the UK, mains electricity is a.c and is generated at 230V
Why is the U.K's mains electricity an alternating current?	it is easier to generate a.c electricity in large amounts. •Many different fuels can be used in power stations.
Why is it more efficient to transmit electricity at high voltages?	•Less energy is lost as heat.
What are transformers?	Transformers are used to step up the voltage at the power station and to step down the voltage near our homes. Transformers only work with an alternating current.
What are motors?	Motors are used in many electrical appliances that makes things move.
What is an electromagnet?	If a wire is made into a coil, the magnetic field pattern becomes similar to that of a bar magnet. This called an electromagnet.
Explain the motor effect.	The motor effect is when a current flows in a wire that is in a magnetic field, the wire experiences a force. If the wire is free to move, it moves. This is called the motor effect.
When is this force at its largest?	When the current is at right angles to the magnetic field lines.
Explain how a transformer works.	•It consists of two separate coils around an iron core. The input voltage is fed into the primary coil, so the output voltage is across the secondary coil.
In a step up transformer, will there be less turns in the secondary coil or the primary coil?	The primary coil will have fewer turns than the secondary coil.

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	Criado por Czean Holgado mais de 7 anos atrás