i) An insulator is a material or object which resists flow of heat (thermal insulator) or electrical charges (electrical insulators). Examples are paraffin, wood, rubber, plastics etc.
ii) Conductors are materials that contain free electrons which carry an electrical charge from one point to another. Examples are metals and non-metals like carbon, graphite etc.
iii) Semi-conductors are materials or objects which allow the flow of electrical heat or energy through them under certain conditions i.e. temperature. Examples are germanium, silicon, cadmium sulphide, gallium arsenide etc.
Mutiso answered the question on October 18, 2018 at 17:21
-
Hazards of radioactivity and their precautions
(Solved)
Hazards of radioactivity and their precautions
Date posted:
October 17, 2018
.
Answers (1)
-
A radioactive element has an initial count rate of 2,400 counts per minute on a scaler. The count rate falls to 300 units per minute...
(Solved)
A radioactive element has an initial count rate of 2,400 counts per minute on a scaler. The count rate falls to 300 units per minute in 30 hours, (a) Calculate the half-life of the element (b) If the initial number of atoms in another sample of the same element is 6.0 × 1020, how many atoms will have decayed in 50 hours?
Date posted:
October 17, 2018
.
Answers (1)
-
The initial number of atoms in a sample is 5.12 × 1020. If the half-life of the sample is 3.0 seconds, determine the number of...
(Solved)
The initial number of atoms in a sample is 5.12 × 1020. If the half-life of the sample is 3.0 seconds, determine the number of atoms that will have decayed after six seconds.
Date posted:
October 17, 2018
.
Answers (1)
-
An isotope has a half-life of 576 hours. Complete the following table and show how mass varies with time from an initial mass of 1280...
(Solved)
An isotope has a half-life of 576 hours. Complete the following table and show how mass varies with time from an initial mass of 1280 g?
Time (hrs)----576--1152--1728---2304
Mass (g)-------640--x------y-----z
Date posted:
October 17, 2018
.
Answers (1)
-
The half-life of a sample of a radioactive substance is 98 minutes. How long does it take for the activity of the sample to reduce...
(Solved)
The half-life of a sample of a radioactive substance is 98 minutes. How long does it take for the activity of the sample to reduce to 1/16th of the original value?
Date posted:
October 17, 2018
.
Answers (1)
-
State the law of radioactive decay
(Solved)
State the law of radioactive decay
Date posted:
October 17, 2018
.
Answers (1)
-
Explain ways of detecting nuclear radiation
(Solved)
Explain ways of detecting nuclear radiation.
Date posted:
October 17, 2018
.
Answers (1)
-
Properties of radioactive emissions
(Solved)
Properties of radioactive emissions
Date posted:
October 17, 2018
.
Answers (1)
-
Sodium has a work function of 2.0 e: Calculate (a) The maximum energy and velocity of the emitted electrons when sodium is Illuminated by...
(Solved)
Sodium has a work function of 2.0 e: Calculate
(a) The maximum energy and velocity of the emitted electrons when sodium is Illuminated by a radiation of wavelength 150 nm.
(b) Determine the least frequency of radiation by which electrons are emitted. (Take ‘h’ = 6.626 × 10-34 Js, e = 1.6 × 10-19, c = 3.0 × 108 m/s and mass of electron = 9.1 × 10-31 kg).
Date posted:
October 17, 2018
.
Answers (1)
-
The threshold frequency for lithium is 5.5 × 1014 Hz. Calculate the work function for lithium. (Take ‘h’ = 6.626 × 10-34 Js)
(Solved)
The threshold frequency for lithium is 5.5 × 1014 Hz. Calculate the work function for lithium. (Take ‘h’ = 6.626 × 10-34 Js)
Date posted:
October 17, 2018
.
Answers (1)
-
The work function of tungsten is 4.52 e V. Find the cut-off potential for photoelectrons when a tungsten surface is illuminated with radiation of wavelength...
(Solved)
The work function of tungsten is 4.52 e V. Find the cut-off potential for photoelectrons when a tungsten surface is illuminated with radiation of wavelength 2.50 × 10-7 m. (Planck’s constant, h = 6.62 × 10-34 Js).
Date posted:
October 17, 2018
.
Answers (1)
-
The cut-off wavelength for a certain material is 3.310 × 10-7 m. What is the cut-off frequency for the material?
(Solved)
The cut-off wavelength for a certain material is 3.310 × 10-7 m. What is the cut-off frequency for the material?
Date posted:
October 17, 2018
.
Answers (1)
-
What is Einstein’s photoelectric equation?
(Solved)
What is Einstein’s photoelectric equation?
Date posted:
October 17, 2018
.
Answers (1)
-
Dangers of X-rays and the precautions
(Solved)
Dangers of X-rays and the precautions.
Date posted:
October 16, 2018
.
Answers (1)
-
An x-ray tube operates at 60 kV and the current through it is 4.0 mA. Calculate the, (a) Number of electrons striking the target per...
(Solved)
An x-ray tube operates at 60 kV and the current through it is 4.0 mA. Calculate the, (a) Number of electrons striking the target per second. (b) Speed of the electrons when they hit the target.
Date posted:
October 16, 2018
.
Answers (1)
-
Determine the energy possessed by X-rays whose frequency is 4 × 1017 Hz.
(Solved)
Determine the energy possessed by X-rays whose frequency is 4 × 1017 Hz.
Date posted:
October 16, 2018
.
Answers (1)
-
Energy changes in X-Ray tube
(Solved)
Energy changes in X-Ray tube
Date posted:
October 16, 2018
.
Answers (1)
-
If the time base control of the CRO is set at 10 milliseconds per cm, what is the frequency of the wave traced given wavelength...
(Solved)
If the time base control of the CRO is set at 10 milliseconds per cm, what is the frequency of the wave traced given wavelength as 1.8 cm?
Date posted:
October 16, 2018
.
Answers (1)
-
Cathode Ray Oscilloscope components and functioning
(Solved)
Cathode Ray Oscilloscope components and functioning.
Date posted:
October 16, 2018
.
Answers (1)
-
What are cathode rays?
(Solved)
What are cathode rays?
Date posted:
October 16, 2018
.
Answers (1)