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Course: Electromagnetism (Essentials) - Class 12th > Unit 6
Lesson 3: Why can birds sit on a high voltage wire?- Circuit components and types of circuit
- Series resistors
- Resistors in parallel
- Parallel resistors (part 3)
- Parallel resistors
- Resistors in series and parallel review
- Finding currents and voltages (pure circuits)
- How can birds sit on high-voltage wires?
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Circuit components and types of circuit
Let's review the components of a circuit and their symbols such as battery, resistor, and switch.
Circuit component definitions and symbols
Resistor ( )
Resistors are electrical components that resist current and expends voltage within a circuit.
Battery ( )
Batteries are electrical components that provide electrical energy.
Batteries have positive and negative terminals. The negative terminal is drawn with a short line, and the positive terminal is shown as a long line.
Switch ( )
Switches turn the flow of current through a circuit pathway on and off. When the switch is open, no current flows because there is a gap in the circuit (Figure 3).
When the switch is closed, current can flow because the circuit is continuous (Figure 4).
Node
A node (or junction) is a place where two or more circuit elements join together. Figure 5 below shows a single node (the black dot) formed by the junction of five electrical components (abstractly represented by orange rectangles).
DC circuit types
Simple circuit
A simple circuit contains the minimum amount of components that allow it to be a functional electric circuit: a voltage source (battery), a resistor , and a loop of wires for current to flow around (see Figure 6 below). We usually ignore any resistance from the wires.
In a simple circuit, the voltage supplied by the battery is the voltage expended by the resistor , and there is only one current in the circuit.
Closed circuit
A closed circuit has a continuous pathway for current to flow through. In other words, there are no gaps in the circuit.
Open circuit
An open circuit has a gap in the circuit that does not allow current to flow through. The gap can be caused by an open switch, a broken component, or broken wire.
Short circuit
A short is a pathway of zero resistance within a circuit (see the blue wire in Figure 9). When there is a short circuit, all the current flows across the short because the current prefers the path of least resistance.
Figure 10 below shows how closing a switch can divert all the current from resistor . When switch is open (see Figure 10A), the current flows out of the positive terminal of the battery towards node . Since the switch is open, no current flows through the switch and all the current flows through resistor . When the switch is closed (see Figure 10B), it forms a short around resistor . Now, once the current reaches , the current bypasses and flows through the switch.
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