A vertical wire carries a current in an upward direction. An electron beam sent horizontally towards the wire will be deflected: 
1. towards right
2. towards left 
3. upwards
4. downwards

A moving charge produces:
1. electric field only
2. magnetic field only
3. both of them
4. none of them

The magnetic field at the origin due to a current element \(i.\vec{dl}\) placed at a position \(\vec r\) is:
(a). \(\frac{\mu_{0} i_{}{}}{4 \pi} \frac{d\vec{l} \times \vec{r}}{r^{3}}\)
(b). \(-\frac{\mu_{0} i_{}{}}{4 \pi} \frac{\vec{r} \times d\vec{l}}{r^{3}}\)
(c). \(\frac{\mu_{0} i_{}{}}{4 \pi} \frac{\vec{r} \times d\vec{l}}{r^{3}}\)
(d). \(-\frac{\mu_{0} i_{}{}}{4 \pi} \frac{d\vec{l} \times \vec{r}}{r^{3}}\)

Choose the correct option: 
1. (a), (b)
2. (b), (c)
3. (c), (d)
4. (a), (d)