The most important operations involving vectors are the ''vector sum'' and the ''vector-scalar product''. As an example of the first, if we are in a train traveling with speed given by one vector, and we throw something inside the train with a velocity, relative to the train, of another vector, the velocity of the object relative to a fixed observer is the sum of those two vectors. As an example of the second, if we double the current through an electromagnet, its magnetic field vector will be multiplied by the number 2. That is, its direction will be unchanged and its magnitude will double. | The most important operations involving vectors are the ''vector sum'' and the ''vector-scalar product''. As an example of the first, if we are in a train traveling with speed given by one vector, and we throw something inside the train with a velocity, relative to the train, of another vector, the velocity of the object relative to a fixed observer is the sum of those two vectors. As an example of the second, if we double the current through an electromagnet, its magnetic field vector will be multiplied by the number 2. That is, its direction will be unchanged and its magnitude will double. |