Which type of motion exists due to the moment of force (couple)?

$A$ couple produces

Which component of torque is responsible for rotation about the $Z$-axis?

$A$ force $\vec{F} = 4\hat{i} + 3\hat{j} + 4\hat{k}$ is applied at the intersection point of the plane $x = 2$ and the $x$-axis. The magnitude of the torque of this force about the point $(2, 3, 4)$ is .......... . (Round off to the nearest integer)

Find the torque of a force $\vec F = -3\hat i + \hat j + 5\hat k$ acting at the point $\vec r = 7\hat i + 3\hat j + \hat k$ with respect to the origin.

The rotational effect is produced by