A radioactive element has a decay constant of 0.077s-1, calculate its half life
12.5s
9.0s
5.1s
0.5s
Correct answer is B
T = \(\frac{0.692}{\lambda} = \frac{0.692}{0.077}\)
= 9s
Which of the following statements is true of ultra violet radiations? It
supports the sensation of hearing
does not cause the emission of electrons from metals
is an electromagnetic wave
is not capable of causing sun burns
Correct answer is C
No explanation has been provided for this answer.
Which of the following statements is not true of the isotopes of an element? They
are atoms of the same element
have the same chemical properties
have the same atomic number
have the same mass number
Correct answer is D
No explanation has been provided for this answer.
Which of the following statements about an electromagnet is not correct?
it is a temporary magnet
its strength depends on the current
its stength depends on the number of turns in its coil
it has permanent poles
Correct answer is D
properties of an electromagnet include, 1) its strength depends on current and the number of turns in the coil,2) it is temporary, 3)it does not have permanent poles, and 4) its direction of flow is determined by the direction of current flowing through the coil.
The direction of induced current in a straight wire placed in magnetic field is determined by using?
Fleming's right hand rule
Maxwell's screw rule
Faraday's law
Lenz's law
Correct answer is D
Lenz's law, in electromagnetism, statement that an induced electric current flows in a direction such that the current opposes the change that induced it.