Alice's Loan Payment (Option 2):
This example shows how a future event can be modeled.
In this case we have modified Alice's loan payment from
Example 1 to include
a one time additional loan payment of $10K at 10 years into the loan.
The problem is repeated below with the added change:
Alice has a loan of $100K dollars at 5% interest rate to pay off.
She wants to pay $500 per month for the first 3 years and then
increase her payment to $550 per month. Alice will make a one time
additional loan payment of $10K at 10 years into the loan. How long
will it take to pay off the loan? Use
Standard Simulation Conditions.
The components G3 and PWL10yr have been added to the circuit from Example 1 to model this extra
payment as shown below. At 10 years (120 months) into the loan, the Voltage Controlled Current
Source, G3, will be turned on to remove 10 coulombs of charge from the capacitor C1.
The PWL10yr component will control timing and amount of current in G3. In this case we turn
on G3 for a short time at 120 months into the loan to remove $10K (or 10 coulombs of charge) from
the loan balance stored at capacitor C1.
We have chosen to run 100 amps in G3 for 0.1 seconds of simulation time to remove this
charge (100amps*0.1sec = 10 coulombs). Since the gain term of G3 is set to 1.0, a
setting at the G3 positive control connection of 100 volts will produce 100 amps of current
flow in G3.
Note that we have allowed 0.02 seconds of simulation time to
turn the G3 current both on and off. In this way, zero transition times at a simulation input is
avoided. Thus to accomplish this one time loan payment, we have set the positive control connection of G3
to have the following voltage versus time relation:
The simulation result is shown below.
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