Exp effect of resistance
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This document describes three experiments on electrical circuits: 1) Measuring current and voltage using 1, 2, and 3 dry cells, finding that more dry cells increase current and voltage. 2) Studying the relationship between resistance and current by measuring current using resistors of 2, 4, 6, and 8 ohms, finding that higher resistance decreases current. 3) Examining the relationship between voltage and current by measuring current using 1, 2, 3, and 4 dry cells, finding that higher voltage increases current.
Exp effect of resistance
- 1. Measurement of electric current and electrical voltage Aim: to measure electric current and voltage Material: dry cell Apparatus: ammeter, voltmeter, battery holder, bulb, bulb socket, switch and connecting wires. Procedure: 1. use one dry cell and set up a circuit as shown in diagram. 2. switch on the circuit. Observe the bulb and ammeter. Record your reading. 3. repeat step 1 and 2 with two and then three dry cells. Make sure the positive terminal of the ammeter/ voltmeter is connected to the positive terminal of the dry cell. Result: Number of dry cell Brightness of bulb Ammeter reading (A) Voltmeter reading (V) 1 Dim 0.25 1.5 2 Bright 0.29 3.0 3 Very bright 0.35 4.5 Conclusion: using more dry cells will increase the amount of current that flows in a circuit and the voltage across the bulb. Title: the effect of resistance on current Aim : To study the relationship between resistance and current Problem statement: what is the effect of resistance change on current? Hypothesis: electrical current will increases when resistance decreases. Variables Manipulated: resistance Responding: ammeter reading/ brightness of bulb Fixed: voltage/ type of wire/ wire thickness
- 2. Apparatus: ammeter, bulb and bulb holder, switch, resistor, connecting wires with clip, dry cell Method: 1. the circuit was set up using the 2 Ω resistor. 2. the switch is switched on and the brightness of bulb was observed. 3. the ammeter reading was recorded. 4. step 1 to 3 were repeated with a 4 Ω, 6 Ω and 8 Ω resistor respectively. Observation: Resistance (Ω) 2 4 6 8 Bulb brightness The brightest Bright Dim The most dim Reading of ammeter (A) 0.9 0.7 0.5 0.3 Discussion: The greater the resistance, the smaller the current flow. As the resistance in the circuit increases, the brightness of the bulb decreases. Conclusion: Electric current decreases when resistance in the circuit increases. The effect of voltage on current Aim: to study the relationship between voltage and current Hypothesis: the higher the voltage, the larger the current that flows in a circuit. Variables: manipulated – number of dry cell responding – current fixed – resistance apparatus: ammeter, voltmeter, bulb, wire, battery, battery holder method: 1. one dry cell was used to set up the circuit as shown in the diagram. 2. the circuit was switched on. The voltmeter and ammeter reading were observed. The results were recorded. 3. steps 1 and 2 were repeated using two, then three and finally four dry cells. Result: Number of Dry cells Voltmeter reading (V) Ammeter reading (A) R = V/I 1
- 3. 2 3 4.4 0.6 4 6.0 0.8 conclusion: the hypothesis accepted. The type of graph obtained is a straight-line graph. Current is directly proportional to voltage. The gradient of the graph shows the ratio of the voltage to current. The ratio is always constant and represents the resistance in a circuit. Low that represent is Ohm’s law Relationship between voltage (V), current (I) and resistance (R) is …………………