Lecture 3: Chapter 2, Part 1 - Classes

2 Electrical Resistance, Ohm’s Law — Section 2.2 in Text
Figure 7 shows the LTspice symbol for a resistor. A resistor is a device that is engineered to resist
the flow of current. The dimensions are controlled according to the following equations. They are
usually made out of carbon, which specifies the value of ρ.
R = ρ ∗ L
(1)
A
The relationship of voltage across and current through a resistor is stated in Ohm’s Law, which is
the following equation.
V = I ∗ R (2)
Figure 7: This is the LTspice symbol for a resistor
3 Nodes, Branches, and Loops — Section 2.3 in Text
Figure 8 is the demonstration circuit using in lecture. There is a single 1.2 volt NiCd battery in the
battery holder. The resistor is 3.3 kΩ. Figure 9 shows a LTspice schematic of this circuit.
Figure 8: This is a photo of a circuit, built using a
breadboard
Figure 9: This is a schematic in LTspice
Figure 10 shows how LTspice can simulate a circuit to solve for voltages and currents.
ENGR 201