Ohm published a paper in April 1826, rewriting Ohm's law as follows: x=ksa/ls is the cross-sectional area of a conductor, k is the conductivity, a is the potential difference between two ends of the conductor, l is the length of the conductor, and x is the current intensity passing through L. If the resistance l'=l/ks is substituted into the above formula, X=a/I' is obtained, which is Ohm's law.
Extended data resistance is a unique property of the load, which is related to the load itself, and the resistance value is determined by the load itself. The resistance value of resistance elements is generally related to temperature, conductor length, cross-sectional area and material. The resistance of most (metals) increases with the increase of temperature, but some semiconductors are the opposite.
Laws of current, voltage and resistance
Series circuit (n electrical appliances in series):
Current: I total = I 1 = I2...= in (in a series circuit, the currents in all parts of the circuit are equal).
Voltage: U total = U 1+U2...+UN (the total voltage is equal to the sum of the voltages of all parts).
Resistance: r total = r 1+R2...+RN (total resistance is equal to the sum of resistances of all parts).
Parallel circuit (n electrical appliances in parallel):
Current: I total = I 1+I 2...+In (in parallel circuit, the main current is equal to the sum of each branch current).
Voltage: Utotal = U 1 = U2...= UN (the voltage at both ends of each branch is equal, which is equal to the power supply voltage).
Resistance: 1/R total =1/r1+1/R2 ...+1/rn (the reciprocal of the total resistance is equal to the sum of the reciprocal of each part). When two electrical appliances are connected in parallel, the following formula is derived: r total = r1r1/(r1+R2).
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