(1) The purpose of connecting R0 in the circuit is to protect the ammeter and prevent it from being burned out when P moves to the rightmost end of R1;
(2) When When I=4mA=0.04A
The total resistance in the circuit R=EI=30.04=75Ω,
The resistance of the resistance wire connected to the circuit R1′=R-R0=75Ω- 30Ω=45Ω
Because L1R1=xR1′
That is, 10300=x45,
The solution is x=1.5cm,
So the spring The extended length △x=L1-x=10cm-1.5cm=8.5cm=8.5×10-2m,
Then the size of the spring elastic force is F=k△x=10000×8.5×10- 2=850N
From the above, F=k[L-L1R1 (EI-R0)]
It can be seen that F and I have a non-linear relationship, and the scale of the ammeter is uniform, so The scale of the tensile gauge is uneven.
(3) The electromotive force of the power supply will decrease after long-term use. When the resistance is the same, the current in the circuit decreases and the deflection angle of the pointer decreases, which will cause the reading of the dynamometer to be too small.
(4) From the expression of F F=k[L-L1R1(EI-R0)], in order to increase the measuring range of the tension meter, the spring with a larger stiffness coefficient can be replaced or the spring with a larger stiffness coefficient can be replaced. Number of turns (or length) of resistor R1.
So the answer is:
(1) The purpose of connecting R0 in the circuit is to protect the ammeter and prevent it from being burned out when P moves to the right end of R1;
(2) 850, no or uneven;
(3) Small
(4) Replace the spring with a larger stiffness coefficient or increase the resistance R1 Number of turns (or length).