Black and White Sketch in Photoshop
Firstly open the image by going to File> open...
and then duplicate it by pressing ctrl+ j (duplicate layer)
With the copied layer selected ...goto image > adjustments> desaturate OR press shift + ctrl + u
then again press ctrl + j (duplicate Layer)...and then press ctrl + i to invert it.
and for this layer select the option Color Dodge in drop down menu of blending options
this should make everything white...
then goto filter > blur > guassian blur and set the radius to any btw 10-20 pixel
the end result looks like this...which looks like a sketch...