Single fixed pulley can be used as a force multiplier.
The above figure shows a single fixed pulley.
When the pulley is not moving, i.e. when in the balanced state,
then load (L) = T and effort (E) = T
So, mechanical advantage (MA) = Load (L)Effort (E)=TT = 1
Since the mechanical advantage is equal to one, so there is not any force multiplication but the direction of the force is changed as the effort is applied in the downward direction but the load is lifted upwards.