1. A uniform magnetic field is directed vertically upwards. In which direction in this field should an alpha particle be projected so that it is deflected south ward? Name and state the rule you have used to find the direction in this case.

1. Fleming's left hand rule

2. It must be projected towards the east

Explanation:

Fleming's left-hand rule states that; When a current-carrying conductor is placed in an external magnetic field, the conductor experiences a force perpendicular to both the field and to the direction of the current flow. This rule was first put forward by John Ambrose Fleming in the later part of the nineteenth century.

Hence if the thumb, fore finger and middle finger of the lefthand are held mutually at right angles to each other; the thumb shows the direction of motion, the fore finger shows the direction of the field while the middle finger shows the direction of the current.

Hence, if the alpha particle is projected eastwards(at right angles) to the uniform magnetic field, it will be deflected southwards in the magnetic field.

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