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Measuring current
Aim : To measure current and voltage in series and parallel circuits.


 * =**Series circuit diagram**= || =**Model/Questions**= || =Parallel circuit diagram= || =Model/Questions= ||
 * [[image:series_circuits.gif width="234" height="70"]]


 * Make a circuit of a bulb with two cells and**
 * two bulbs at a normal brightness.** || Measure the current of each circuit. What happens to the amount of current as you increase the number of bulbs in series?

Current __ stays the same although we add more number of bulbs in series. __ || media type="custom" key="8997704" [|Circuit construction kit DC only in Phet] || What happens to the amount of current as you increase the number of bulbs in parallel?

Current __ decrease __ as we add more bulbs in parallel circuit. Current becomes __ 1/2 or half __ then __ 1/3 __ as we increase the number of bulbs from 1 to 2 and 3 respectively. ||
 * [[image:2_bulbs_in_series.gif width="177" height="171"]] || [[image:2bulbs_in_series_model.gif width="171" height="194"]] || [[image:2bulbs_in_parallel.gif width="139" height="177"]] || [[image:2bulbs_in_parallel_model.gif width="202" height="222"]] ||
 * ===Draw a circuit diagram with 3 bulbs in series=== || What's the measurement of voltage across each bulb in series circuit?

It is __ the amount of a fraction of the number of bulbs in the circuit. __ || || What's the measurement of the voltage across each bulb in parallel circuit?

It is __ the same across each bulb. __ ||
 * ===**Draw a circuit diagram with 4 bulbs in series**===

Click to see the answer || What happens to the brightness of the bulbs as you add up more lamps in series.

It __ gets dimmer and dimmer as you increase the number of bulbs __ in series. || || What happens to the brightness of the bulbs as you add up more lamps in parallel?

It __ stays the same brightness although we add the bulbs up __ in parallel. ||

= = =**Simple circuits**=

Is there a unit in your result? For each circuit, write the ammeter readings down in the back of your jotter book.

If you still have time to do more experiments; 1. Make a circuit of a bulb with three cells and three bulbs in series at a normal brightness. 2. Make a circuit of a bulb with three cells and one bulb in each branch in parallel circuit. 3. Which circuit of a bulb is brighter?

CONCLUSION FOR SERIES AND PARALLEL CIRCUITS ACTIVITY
 * 1) **What can you say about the current in a series circuit?**
 * 2) **What about the currents in the different wires of a branching circuit?**
 * 3) **What happens to the current if you replace a 10Ω bulb with a 10Ω resistor?**
 * 4) What are the different energy changes in the bulb and resistor?
 * 5) **What happens to the current in a circuit if you add a battery in parallel with another battery?**
 * 6) **What happens to the current in a circuit if you add a battery in series with another battery?**
 * 7) **What happens to the current in a component when you add others in series?**
 * 8) **What happens to the current in a component when you add others in parallel?**

**Series and parallel**
In a series circuit every component is on one branch of the circuit. In Series circuit, the current that flow through each of the components is the same. If one bulb in a series circuit is removed or broken, the remaining bulbs do not light up.

In a parallel circuit there is more than one branch. In a parallel circuit, the current in each branch adds up to the total current. When current reaches a branch some currents flow into each branch

**Measuring Current 1**
In a __ series __ circuit, if one bulb "blows" __the whole circuit doesn't light up__. In a __ parallel __ circuit, only the __bulbs in the same branch__ are affected. In our houses, lights are connected in a __ parallel __ circuit.
 * Fill in the blanks below either with serious or parallel.**

**Measuring Current 2**
In a parallel circuit the current flowing in each branch is the same as the total current in the main branch.

Explorelearning circuits

=** Resistance: **= The opposition to current in a circuit is called the re....................... .

The greater the resistance in a circuit, the lower the current. It is measured in ohm.
The longer the wire the m................. the resistance and the l................. the current. There are two kinds of resistors - Fixed resistors, Variable resistors (or Rheostats) =V=IR=

The current increases when the resistance decreases.
= = =Diagram= = = =Conclusion= What happens to the current/resistance in the series circuit as you add up more number of bulbs? What happens to the current/resistance in the parallel circuit as you add up more number of bulbs? What patterns in resistance have you found in the series and the parallel circuit?
 * Aim : To investigate resistance in a series and parallel circuit. **
 * = Total voltage used ||= Series ||= Series ||= Parallel ||= Parallel ||
 * = The number of bulbs ||= Current ||= Resistance ||= Current ||= Resistance ||
 * = 1 ||=  ||=   ||=   ||=   ||
 * = 2 ||=  ||=   ||=   ||=   ||
 * = 3 ||=  ||=   ||=   ||=   ||
 * = 4 ||=  ||=   ||=   ||=   ||


 * = Total voltage used:10V ||= Series ||= Series ||= Parallel ||= Parallel ||
 * = The number of bulbs ||= Current ||= Resistance ||= Current ||= Resistance ||
 * = 1 || 1A || 10ohm || 1A || 10ohm ||
 * = 2 || 0.5A || 10+10 || 2A || 1/[(1/10)+(1/10)] ||
 * = 3 || 0.33A || 10+10+10 || 3A || 1/[(1/10)+(1/10)+(1/10)] ||
 * = 4 || 0.25A || 10+10+10+10 || 4A || 1/[(1/10)+(1/10)+(1/10)+(1/10)] ||

For resistors in series, the r_ to flow of electrical charges **incereases/decreases** as more resistors are a_; The current in the circuit _. R(Total)= For resistors in parallel, c_ from the electric cell __d_____s__ among the resistors as more resistors are added; The current in the circuit _. R(Total) =

For resistors in series, the resistance to flow of electrical charges increases as more resistors are added; The current in the circuit decreases. R(Total)=R 1 +R 2 +R 3 For resistors in parallel, current from the electric cell divides among the resistors as more resistors are added; The current in the circuit increases. 1/R(Total) =1/R 1 +1/R 2 +1/R 3

The reciprocal of the total resistance is the sum of the reciprocals of each one of the resistance.