Class 12 NEET Physics Current Electricity Questions Part 1

Lower resistance on extreme left and upper resistance on extreme right are ineffective. The resistance R2 and R3 are in series combination. Therefore their equivalent resistance,
R′=R2+R3 =10+10=20Ω
Similarly, the resistance R5 and R6 are in series combination. Therefore their equivalent resistance,
R"=R5+R6 =10+10=20Ω
Now the equivalent resistances R′ and R" are in parallel combination. Therefore their equivalent resistance,
R"′=

R′R"

R′+R"

=

20×20

20+20

=

400

40

=10Ω
Thus equivalent resistance between A and D,
R=R1+R"′+R4 =10+10+10=30Ω(∵ series combination )