Parallel and Series Circuits
Electrical devices can be connected in two different ways in a circuit.
1) In series
2) In parallel
Series Circuits
R_{total} = R_{1} + R_{2}
- The current is the same through each resistor.
- The voltage splits up.
- Total resistance exceeds the highest resistance of the resistors.
Parallel Circuits
1/R_{total} = 1/R_{1} + 1/R_{2}
- The voltage is the same through each resistor.
- The current splits up.
- Total resistance is less than the lowest resistance of the resistors
In the following circuit, the resistors are in red. Put in the values that you deal with in Red boxes. Treat the boxes as if they were real resistors, in doing so, and then calculate the total resistance.
Resistance Calculator
R = Ω
Please answer the following questions.
- The
dimensions of a solid iron cuboid are 6cm, 4cm and 2cm respectively. If the
resistivity of the substance is 0.002 units, find the resistance in the
following cases:
- If the current enters through the smallest
surface
- If the current enters through the largest
surface
- Explain the following:
- The copper cable of a lightning conductor
is very thick
- The wire inside a hair dryer is thin and
long
- The
resistance of a piece of wire is 9 Ohms. Find the new resistance, if it is
folded in two and then twisted.
- Can
Ohm’s law be applied to a light bulb which is hotter when in use, as the
physical conditions do not seem to be constant?
- You
are provided with three resistors of 12 Ohms each. How many different
combinations can be obtained from them? Calculate the total resistance in each
case.
- If two
resistors are connected in series the total resistance is 25 Ohms and if they
are connected in parallel the resistance is 6 Ohms. Find the resistance of
each.
- The
power of a light bulb is 60W at 240V. What is its new power if the voltage is
dropped down to 200V?
- Explain as to why the electricity is transmitted at a very high
voltage through thick copper cables through large distances.
- If a 2
kW kettle is used 2 hours a day for a period of one month, how many kWh are used
up?
- Explain the following:
- A switch is always connected across the
live wire
- TV does not need an earth wire
- Ammeters are connected in series whereas
voltmeters are connected in parallel