Physics retrieval-roulette
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QuestionAnswer
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What is acceleration?Rate of change of an object's velocity.1Forces
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What is air resistance?The force exerted on an object by the air, when it moves through it.2Forces
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What is average speed?The distance moved by an object divided by the time taken for this to happen. Scalar3Forces
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What is displacement?The length and direction of the straight line from the initial position of an object to its position at a later time. Vector4Forces
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What is distance?The length of the path along which an object moves. scalar.5Forces
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What is a distance-time graph?
A way of summarising the motion of an object by showing how far it has moved from its starting point at every instant during its journey.
6Forces
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Define a forceA push or a pull.7Forces
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Define a non contact forceA force that involves objects that are not physically touching8Forces
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Define frictionA force that opposes motion between two surfaces that are in contact9Forces
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Define an interaction pairA pair of forces that are equal in strength, but opposite in direction.10Forces
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Define instantaneous speedThe rate at which an object is moving at a given moment in time.11Forces
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Define kinetic energyThe energy that something has owing to its motion.12Forces
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Define momentumA property of any moving object. Mass x Velocity13Forces
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Define reaction as a force The force exerted by a hard surface on an object that presses on it.14Forces
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What is a resultant force?The sum, taking their directions into account, of all the forces acting on an object.15Forces
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What is velocity?Speed in a given direction.16Forces
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What is a velocity-time graph?A graph that can be used to plot the velocity of an object versus time.17Forces
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What are contact forces?A force that involves objects that are physically touching18Forces
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What is a scalar quantity?Only has a magnitude19Forces
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What is a vector quantity?Has a magnitude and a direction20Forces
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What is Acceleration?change in velocity over time. Vector21Forces
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What is the uniform acceleration of a falling object under gravity
10 m/s/s22Forces
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Define weightThe affect of gravity on mass. On earth 10N/Kg23Forces
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Define massthe amount of matter in an object24Forces
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What is newtons first law?If the resultant force is 0 - the object remains stationary or is travelling at a constant speed25Forces
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What is newtons second law?F = ma26Forces
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What is newtons third law?For every action there is an equal sized force in the opposite direction27Forces
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Define Inertiathe property of an object to remain in a constant state unless acted on by an external resultant force28Forces
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What is the braking distance?The distance it takes to brake and stop29Forces
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What is the thinking distance?The distance it takes to react and press the brake pedal30Forces
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What is the Stopping distance?Braking distance + thinking distance31Forces
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What is static electricity?
The separation of electric charge caused by rubbing two objects together, as electrons are transferred from one to the other. The object gaining electrons becomes negatively charged, and the object losing electrons becomes positively charged.
32Electricity
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What happens when charged materials are brought together?
If the materials have the same charge, they repel each other; if the materials have different charges, they attract each other.
33Electricity
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What is an electric current?Rate flow of charge, measured in amps.34Electricity
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What happens in an electric circuit?
The wires & components have free electrons, which move because the cell has a positive terminal and a negative terminal (making a potential difference). These charges are never used up, as they flow in a continuous loop.
35Electricity
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What are conductors?
Substances or objects which allow electrical currents to pass through, because they have lots of free charges. Metals are an example, because they contain free electrons, which can move with the current.
36Electricity
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What are insulators?Substances or objects which don't allow electrical currents to pass through, because there are no charges free to move.37Electricity
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How are components in circuits shown?Using the standard symbols for the particular components.38Electricity
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What is an alternating current (H)?
a.c. changes direction (back and forth) continuously. It is used for the mains supply, because it is easier to generate and distribute, more efficient, and can be used in a transformer.
39Electricity
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What is a direct current?d.c. always flows in the same direction as the positive and negative terminals of the cell do not change40Electricity
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At what voltage is the mains supply?230 volts.41Electricity
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What is potential difference?
The work done on or by a given amount of charge between two points on a circuit (voltage), measured in volts with a voltmeter.
42Electricity
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What happens in a series circuit when more batteries are added?
The EMF and current increase.43Electricity
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What happens in a parallel circuit when more batteries are added?
The potential difference and current stays the same, but the current supplied by a single cell decreases. The cells will last longer.
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What is the effect of adding components to a circuit?
Components, such as resistors, lamps and motors, resist the flow of charge in a circuit. This increases the resistance in the circuit, and decreases the current.
45Electricity
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What happens when resistors are added to series circuits?The resistance increases, because the battery is having to push charges through more resistors.46Electricity
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What happens when resistors are added to parallel circuits (H)?
The overall resistances reduces and the current increases, because there are more paths along which the charges can flow.
47Electricity
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What happens when an electric current flows through a component (H)?
The charges in the current lose energy as they collide with vibrating ions in the wire, which is transferred to the component. This causes the component to heat up, and can make a light glow, for example.
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What is the formula for resistance?Resistance (ohms) = Voltage (volts, V) / Current (amperes, A).49Electricity
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What is the relationship between the current through and voltage across a resistor?
No matter what direction the current is flowing in, if the resistor's resistance stays constant, the current through and voltage across it are directly proportional (as one increases, so does the other).
50Electricity
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What does a voltage-current graph for a fixed resistor look like?
A straight line in a positive direction, passing through the origin.51Electricity
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What is the effect of temperature on a thermistor?As temperature increases, the thermistor's resistance decreases, and the current flowing through it increases.52Electricity
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What is the effect of light intensity on a light dependent resistor?
As light intensity increases, the LDR's resistance decreases, and the current flowing through it increases.53Electricity
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What happens when two or more components are connected in a series to a battery?
The current flowing through each component is the same; the total potential difference across all the components is equal to the potential difference across the battery; the potential difference is largest across the components with the greatest resistance.
54Electricity
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What happens in a series circuit when the resistance in one component changes?
The potential difference across all components will change.55Electricity
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What is the relationship between the work done on the charges in the circuit and on the circuit components?
The work done on each charge in the circuit by the battery is equal to that on the circuit components. A charge moving through a large resistance has more work done on it than one moving through a small resistance.
56Electricity
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What happens in a parallel circuit with one component in each parallel path (H)?
The current flowing through each component is based on the resistance of the components; the component with the smallest resistance has the greatest current flowing through it; the total current running from the battery back into the battery is equal to the current flowing through each of the parallel components.
57Electricity
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What happens when more components are added to a parallel circuit (H)?
The current flowing through each component stays the same, and the current through the battery increases.58Electricity
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What is the effect of voltage on current and through components on a parallel circuit (H)?
The same voltage level causes more current to flow through a smaller amount of resistance than a bigger one.59Electricity
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What is the relationship between the potential difference across each component in a parallel circuit and the battery (H)?
The potential difference across each component is equal to the potential difference of the battery.60Electricity
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What is electromagnetic induction?
A current being induced by a magnet. The magnet is moved into a coil of a wire, and a voltage is induced between the ends of the wire as the magnetic field is cut. Joining the two ends together makes a current, as the circuit has been completed.
61Electricity
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How can the direction of an electromagnetic current be changed?
Removing the magnet from the coil or moving the other pole (N/S) into the coil can induce a current in the .opposite direction to the current flow
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How can electromagnetic induction be used?In generators, which produce electricity for the mains.63Electricity
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How does a generator work?
A magnet rotates inside the coil, and the voltage induced in the coil changes in direction and size, based on the position of the poles. This produces an alternating current, as the direction of voltage and current is reversed every half turn. After a full turn, the current and voltage are both flowing in the same direction as originally.
64Electricity
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How can the voltage in a generator be increased?
Increasing the speed of the rotation of the magnet; increasing the strength of the magnetic field, e.g. with an electromagnet; increasing the number of turns on the coil; giving the coil an iron core.
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What is power?
A measure of the rate of energy transfer to an appliance or device and its surroundings, as work is done by the power supply on the appliance or device as an electric charge flows through it. It is measured in watts.
66Electricity
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What is the formula for power?Power (watts, W) = Voltage (volts, V) X Current (amperes, A).67Electricity
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What is a transformer?
A device, with two wire coils (primary and secondary) wrapped around an iron core, which is used to change the voltage of an alternating current.
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How does a transformer work (H)?
The two coils are placed close together, and the alternating current in the primary coil creates an alternating magnetic field. This, in turn, induces an alternating current in the secondary coil.
69Electricity
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How is the change in voltage by a transformer determined (H)?
By the number of turns on the coils. Voltage on primary coil (Vp) / Voltage on secondary coil (Vs) = Number of turns on primary coil (Np) / Number of turns on secondary coil (Ns).
70Electricity
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What is an electric motor?
A coil of wire, which rotates in between the opposite poles of a permanent magnet, when a current flows through the coil.
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How does a current-carrying wire work with a permanent magnet?
The wire can exert a force on the magnet (or another current-carrying wire). It also experiences a force inside a magnetic field, if the field's lines of force are at right angles to the wire (the force will be at right angles to the current direction and the lines of force from the magnetic field).
72Electricity
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What happens when a current flows through the coil in a magnetic field?
The current will cut the magnetic field lines in opposite directions on each side of the coil. The field lines nearest the South pole of the magnet will be cut in the same direction, and those nearest the North pole in the opposite direction. This creates a pair of opposing forces with constant directions, giving continuous rotation.
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What is a commutator?
A rotary switch, which turns with the coil in an electric motor, but the brushes touching it remain fixed. This ensures that, as the coil rotates, the direction of current into it is fixed.
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How can an electric motor be used?Hard drive disks, DVD players, electric motor vehicles, washing machines, tumble dryers, microwave ovens.75Electricity
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What are the seven type of radiation that make up the electromagnetic spectrum?
) Radio waves, 2) Micro Waves 3) Infra Red 4) Visible Light 5) Ultra Violet 6) X-rays 7) Gamma Rays76Waves
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What does the amount of energy carried by a photon depend on?
The frequency of the radiation77Waves
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What happens to the frequency and energy as you go along the electromagnetic spectrum?
Increases -Radio wave photons have the lowest frequency and the least energy whereas gamma ray photons have the highest frequency and the most energy
78Waves
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What do you call any object that emits radiation?A source79Waves
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What speed does electromagnetic radiation travel at?The 'speed of light' -300,000 km/s -3.0 x 10^8 m/s80Waves
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What happens when the radiation emitted from a source?Spreads out until it reaches some matter81Waves
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Once radiation reaches some matter, what three things can then happen?
Radiation might: -Be transmitted (just keep going),-Be reflected (bounce back) -Be absorbed82Waves
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What are detectors?Objects that absorb radiation83Waves
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What is meant by the intensity of radiation?How much energy arrives at each square metre of surface per second84Waves
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What the units of intensity?W/m^2 - watts per square metre85Waves
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What is ionisation?
When radiation hits an atom or molecule, it can sometimes have enough energy to remove an electron and change the atom or molecule
86Waves
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What are the types of radiation that can cause ionisation?-Ultraviolet, X-Rays and gamma rays87Waves
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What happens if your cells are exposed to ionising radiation?
The damage to DNA molecules can cause mutations and the cells might start dividing over and over without stopping (cancer)
88Waves
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What can lead to sunburn or skin cancer?Ultraviolet radiation from the Sun. UV radiation is ionising. -Can damage living cells in the skin.89Waves
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How can you protect yourself from X-Rays?
Radiographers may wear Lead aprons or stand behind concrete walls. Lead absorbs x-Rays (protects from unnecessary exposure). Lead shield over parts of the body that aren't being investigated
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What happens when non-ionising radiation is absorbed by a substance?
Transfers energy to the atoms or molecules of the substance. -Heats them up91Waves
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How do microwave ovens heat up food?
Microwaves make particles vibrate, heating them up. -Some waves strongly absorbed by water molecules. -heats things containing water (there's water in all food substances)
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What are microwaves used for?To send signals between mobile phones and mobile phone masts93Waves
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Why are there some health risks with using microwaves?
Phone emits microwave radiation. Some radiation is absorbed by your body and causes heating of your body tissues. Concerns that heating tissues (like brain and jaw) could increase medical conditions like cancer
94Waves
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What is most of the radiation emitted from Earth?Infrared radiation -heat95Waves
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What is electric current?A flow of electric charge.96Magnetism
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What is Magnetic field?the region around a magnet where the magnetic force is exerted97Magnetism
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What is the Magnetic Pole?The ends of a magnetic object, where the magnetic force is strongest.98Magnetism
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current carrying wireAn electric current produces a magnetic field around it99Magnetism
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