Demos: 6C-06 Growth & Decay of Current in an Inductance


A resistance and an inductance (having the same DC resistance) are connected to a battery separately. The final current in each circuit is the same, but the current rises and decays very slowly through the inductor.

Directions: When switch S2 is in the position shown in the diagram, the battery is connected in the circuit. Switch S1 determines whether the current is through the resistor or the inductor. When switch S2 is in the other position, the battery is taken out of the circuit and the circuit is “shorted.”

Suggestions for Presentation: Let the students know that the DC resistance of the resistor and the inductor are the same. (An ohmmeter can be used to show this, if you wish.) Ask what difference, if any, there would be in the current if the inductor or the resistance is in the circuit, respectively. (Remind them that the resistances are the same.) First choose the resistor branch. The full current will be “immediate.” Then switch to the inductor. The final current will be the same, but it will take a noticeable time for it to reach that value. Similarly, when the switch S2 is put in the “short” position, the current drops to zero instantly in the R circuit but very slowly in the L circuit. Discuss why this should be so.

Applications:

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Last Updated: May 9, 2016 11:44 AM