your friend says that the equivalent (combined) resistance of resistors connected in series is always more than the resistance of the largest resistor. Dou you agree?
Yes, I agree.
It is hard to build a negative resistance.
No, I don't agree with that statement. When resistors are connected in series, the equivalent resistance is actually equal to the sum of the individual resistances.
To calculate the equivalent resistance of resistors connected in series, you simply add up the resistance values. The total resistance is given by the formula:
R_eq = R1 + R2 + R3 + ... + Rn
Where R_eq is the equivalent resistance and R1, R2, R3, and Rn are the resistances of the individual resistors.
So, in a series circuit, the total resistance will never be greater than the resistance of the largest resistor. It can be equal to or lower than the resistance of the largest resistor, depending on the values of the other resistors in the circuit.
To confirm this, you can calculate the equivalent resistance by adding up the resistance values of the resistors in series.