Question

drawing circuits
look at the circuits below
name:

1. which circuit do you think is a parallel circuit and which circuit is a series circuit?
2. how are the two circuits different? explain.

now, draw each of the circuits described, using proper circuit symbols.
a dry cell running three lights and a motor in series.
a three cell battery running two motors in parallel.

Explanation:

1. In a series circuit, components are connected end - to - end so that there is only one path for current to flow. In a parallel circuit, components are connected across the same two points, creating multiple paths for current. Looking at the given circuits, the left - hand circuit has components (assuming the symbols are for resistors or bulbs) in a single loop (one path), so it is a series circuit. The right - hand circuit has components connected across the same two points (multiple paths), so it is a parallel circuit.
2. Series circuit:

• Current: The same current flows through all components ($I = I_1=I_2=\cdots=I_n$).
• Voltage: The total voltage of the source is divided among the components ($V = V_1 + V_2+\cdots+V_n$).
• Resistance: The equivalent resistance is the sum of individual resistances ($R_{eq}=R_1 + R_2+\cdots+R_n$).

Parallel circuit:

• Current: The total current is the sum of the currents through each parallel branch ($I = I_1+I_2+\cdots+I_n$).
• Voltage: The same voltage is across each component ($V = V_1 = V_2=\cdots=V_n$).
• Resistance: The reciprocal of the equivalent resistance is the sum of the reciprocals of individual resistances ($\frac{1}{R_{eq}}=\frac{1}{R_1}+\frac{1}{R_2}+\cdots+\frac{1}{R_n}$).

For drawing the circuits:

• For a dry cell running three lights (represented by $\bigcirc$) and a motor (represented by $M$) in series: Draw a single loop with the dry cell (two parallel lines, longer line for positive), then connect the three lights and the motor one after another in the loop.
• For a three - cell battery (three sets of two parallel lines, longer lines for positive, connected in series) running two motors ($M$) in parallel: Draw the three - cell battery. Then, from the positive terminal of the battery, have two branches. In each branch, connect a motor, and then connect the branches back to the negative terminal of the battery.

Answer:

1. The left - hand circuit is a series circuit and the right - hand circuit is a parallel circuit.
2. Series circuit: Same current through components, voltage divides among components, equivalent resistance is sum of resistances. Parallel circuit: Same voltage across components, total current is sum of branch currents, reciprocal of equivalent resistance is sum of reciprocals of resistances.

For drawing:

• Series circuit (dry cell, three lights, motor): Single - loop circuit with components connected end - to - end.
• Parallel circuit (three - cell battery, two motors): Two motor branches connected across the battery.