Which is true about the inductance of a solenoid?
o it depends on the number of turns per unit length but not on the area of each turn.
o it depends on the area of each turn but not on the number of turns per unit length.
o it depends on the number of turns per unit length and the area of each turn.

Explanation:

The inductance of a long solenoid can be approximated by:

Where:

Therefore, according to this, we can conclude that  the inductance of a solenoid depends on the number of turns per unit length and the area of each turn.

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

a and b sometimes have a positive value