A negative charge is moving across a room from south to north. A magnetic field runs from east to west. In what direction is the magnetic force on the moving negative charge?

Downwards

Explanation:

Using Fleming's right hand rule, where the middle finger represents the negative charge moving in the south to north direction, the fore finger represents the magnetic field which points in the east to west direction.

If we are to follow this orientation and place the thumb, middle finger and fore-finger at right angles to each other, the thumb represents the direction of the magnetic force on the charge.

In this case, the magnetic force points downwards after setting the other orientations of the magnetic field and the negative charge's direction.

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.