F
Farad
The farad (F) is the SI Unit of capacitance.
Fahrenheit scale of temperature
On the Fahrenheit scale, the ice point, the ice point (lower fixed point) is taken as 32? F and the steam point (upper fixed point) is taken as 212 deg F. The interval between these two points is divided into 180 equal divisions. Thus, unit division on the Fahrenheit scale is 1deg F. The temperatures on the Celsius scale and the Fahrenheit scale are related by the relationship, C/100 = (F - 32) / 180. The temperature of a normal healthy person is 37 deg C or 98.6 deg F.
Fibrescope
Fibrescope are sometimes called endoscopes. A flexible fiber-optic instrument used to view an object or area, such as a body cavity, that would otherwise be inaccessible.
Field
A property of a point in space describing the forces that would be exerted on a particle if it was there.
Filament Lamp
These lamps rely on an incandescent metal filament to produce light. The interior of the lamp is filled with an inert gas in order to stop the filament from corroding. An electrical current, passed through the filament makes it extremely hot. When sufficiently hot, the filament itself will emit light radiation. Tungsten metal is chosen for the filament due to its high melting point of about 3956 Celsius.
First law of motion
Every object remains at rest or in a state of uniform straight-line motion unless acted on by an unbalanced force.
Fission Process
This usually refers to nuclear fission, where an atomic nucleus splits apart into smaller pieces. Fission should not be confused with fusion. When a heavy, unstable nucleus undergoes fission, energy is released as heat. In nuclear power stations, uranium is often used as the fissile material, where a nuclear chain reaction is controlled to release energy.
Flex
The flex allows electrical current to flow into domestic appliances from the mains socket. The flex should be correctly wired to a plug.
Fluids
Matter that has the ability to flow or be poured; the individual molecules of a fluid are able to move, rolling over or by one another.
Fluid friction
A friction force in which at least one of the object is a fluid (i.e. either a gas or a liquid).
Fluorescent Lamps
These lamps produce light by passing electrical current through a mercury vapour at low pressure. The electrical current excites ("energises") the electrons of the mercury atoms. These electrons quickly give up their energy as light. The light which is produced is invisible ultra-violet and would be useless. To get round this problem, the inside of the tube is coated with fluorescent paint, which converts U.V. light to visible light.
Fluorescent lamps are more efficient than filament lamps as they waste less energy as heat.
Focal Length
The focal length of lens is measured in meters. It is the distance from the centre of the lens to the point at which rays passing through the lens meet (i.e. focus). It is related to lens power.
Force
Forces can cause an object to speed up, slow down, change direction or change shape (if they are unbalanced). Forces are either push forces or pull forces. Force is a vector quantity.The SI unit of force is the newton,denoted by N.
Force of gravitation
The force with which two objects attract each other by virtue of their masses is called the force of gravitation. The force of attraction acts even if the two objects are not connected to each other. It is an action-at-a-distance force.
Fossil Fuel
Fossil fuels are coal, oil and gas. They are non-renewable resources. Fossil fuels come from ancient remains of plants and animals, compressed and heated over many millenia. The combustion of fossil fuels is now (nearly) universally accepted as causing global warming. They are well known to produce acid rain. Most of the world's energy is still produced from fossil fuel.
Fracture strain
An adjustment to stress in which materials crack or break as a result of the stress.
Free fall
The motion of a body towards the earth when no other force except the force of gravity acts on it is called free fall. All freely falling bodies are weightless.
Freezing point
The temperature at which a phase change of liquid to solid takes place; the same temperature as the melting point for a given substance.
Frequency
The frequency of a regular event is the number of times the event occurs in a given time.The SI unit of frequency is the hertz (Hz) (equivalent to 'per second' or s-1).
Frequency (of waves)
The number of waves produced per second is called its frequency.
Frequency (of oscillations)
The number of oscillations made by an oscillating body per second is called the frequency.
Frequency Modulation
Frequency modulation refers to the changing of the frequency of a radio-frequency or microwave frequency carrier wave. The other method of modulation is called amplitude modulation.
Friction
Friction is a force which tends to make moving objects slow down. Friction also prevents objects from slipping over one another. Friction due to fluid flow is called drag.
Fridge
A fridge is an example of a heat pump. It extracts heat energy from inside the fridge cabinet and releases it into the room. The basic principle relies on the latent heat of vaporisation of a coolant liquid. The coolant is evaporated within the pipes inside the cabinet - the heat required for this is taken from the cabinet itself, with the result that the cabinet becomes cooler.
Fuel rod
Long zirconium alloy tubes containing fissionable material for use in a nuclear reactor.
Fundamental charge
Smallest common charge known; the magnitude of the charge of an electron and a proton, which is 1.60 x 10^-19 coulomb.
Fundamental frequency
The lowest frequency (longest wavelength) that can set up standing waves in an air column or on a string.
Fundamental properties
A property that cannot be defined in simpler terms other than to describe how it is measured; the fundamental properties are length, mass, time, and charge.
Fuse
A fuse, where fitted, is designed to protect the flex (and not the appliance) from current overload and the associated risk of fire. The fuse rating should always be less than that of the flex which it is protecting. This will make sure that it blows before the flex melts. If the fuse in the plug blows, it is likely to be because of a fault in the appliance which is drawing too much current.
The fuse (and switch) should always be connected to the live wire in a plug.
Fusion
A nuclear reaction in which two nuclei stick together to form one bigger nucleus.