JEE Main 2014 · 6 Apr · Shift 1, Physics question 28

A diode is forward biased when its anode (the triangle's side) is at a higher potential than its cathode. In every option the anode is on the left.

• (1): $+2$ V to $-2$ V. Forward.
• (2): equal potentials. No bias.
• (3) and (4): the left end is lower. Reverse.

So the answer is (1).