#p2.5

[doitvision]

P1.5, P2, P2.5, P3 LED Wall/LED Screen,Which I Need to Prefer?

Difference P1.5,P2,P2.5 and P3.91 led video wall?how to choose the HD led video wall for my indoor events?which is better 2mm,3mm,led display?

[sansibestleddisplay-blog]

P2.5 indoor LED retail ads display, widely used in diverse areas to attract people’s attention. And Deliver specific info to your potential customers. 

[phychembi]

2.5 know and use the relationship: power = current x voltage, and apply the relationship to the selection of appropriate fuses

power (W) = current (A) x voltage (V)

for example, if a light has a voltage of 6V and a current of 2A, the power of the light is 12W. 

fuse markings will generally show the voltage and current of the device, and the power can therefore be deduced from this information

[iamrevisinghonest-gcse]

Atoms and Radiation

Radioactive substances are substances that constantly give out radiation from their nuclei, no matter what is done to them.

Background radiation comes from various different sources, including natural ones such as rocks and cosmic rays from space, and man-made ones such as the fallout from nuclear accidents and weapons tests.

An alpha particle consists of two protons and two neutrons (the same as a helium nucleus).

A beta particle is an electron from the nucleus.

Gamma radiation is a form of electromagnetic radiation.

Alpha and beta particles are deflected by electric and magnetic fields; gamma radiation is not.

The half-life of a radioactive isotope is the average time it takes for the number of nuclei of the isotope in a sample to decrease to half of its original number or for the rate of radiation from a sample to decrease to half of its original level.

[iamrevisinghonest-gcse]

Atomic Structure

An atom consists of a central nucleus (containing protons and neutrons), around which are electrons.

Protons are positively charged; electrons are negatively charged; neutrons are neutral (have no electrical charge).

An atom has no overall electrical charge. It has the same number of protons as electrons.

Atoms can lose or gain electrons. This changes them into ions (charged particles).

Atoms of the same element always have the same number of protons. However, they can have different numbers of neutrons, making different isotopes.

The atomic number of an atom is the total number of protons in its nucleus.

The mass number of an atom is the total number of protons and neutrons in its nucleus. (Due to having such a small mass that it is negligible, electrons are not included in the mass.)

[iamrevisinghonest-gcse]

What Happens when Radioactive Substances Decay and the Uses and Dangers of their Emissions

Radioactive substances constantly emit radiation from the nuclei of their atoms. These nuclear radiations can be very useful, but also very dangerous. It is important that we understand all the properties of different types of nuclear radiation.

In order to understand what happens to radioactive substances when they decay, we need to understand the structure of the atoms from which they are made.

The use of radioactive substances is dependent on their penetrating power and half-life.

You should be able to use your skills, knowledge and understanding to:

Evaluate the effect of occupation and/or location on the level of background radiation and radiation dose

Evaluate the possible hazards associated with the use of different types of nuclear radiation

Evaluate measures that can be taken to reduce exposure to nuclear radiation

Evaluate the appropriateness of radioactive substances for particular uses in terms of the radiation emitted and their half-lives

Explain how results from the Rutherford and Marsden scattering experiments led to the "plum pudding" model of the atom being replaced with the nuclear model.

Practical work to develop your skills and understanding:

Demonstrating the "plum pudding" model of the atom, e.g. using hot cross buns

Demonstrating probabilities regarding half-life, e.g. using dice

Measuring the penetration and range of the radiation from different sources using Geiger counters.