Y9 Physics 1 – Electricity Questions & Answers

Y9 Physics 1 – Electricity Questions & Answers A piece of uniform wire has a resistance of 3.0Ω. What is the resistance of a similar piece of wire but 4 times as long? - ANSWER: R = 3.0Ω x 4 = 12.0Ω A piece of uniform wire has a resistance of 4.0 ohms. Calculate the resistance of a similar piece of wire with 2 times the length and 3 times the cross sectional area. - ANSWER: R= 4.0Ω x (2/3) = 2.67Ω (3 s.f.) Convert 3.0 mA to A - ANSWER: 0.003 A (divide by 1000) Does a filament of a light bulb obey ohms law? - ANSWER: Yes, the reason that the graph of V against I is not linear is because there has been a significant increase in the temperature of the filament (as the voltage and current have increased). Ohms law tells us to expect a straight line graph of V against I for a CONDUCTOR only if the temperature remains constant Does supply voltage divide in parallel? - ANSWER: No Fill in the blanks: the resistance of a conductor is ________ ____________ to the length of the conductor - ANSWER: Directly proportional Fill in the blanks: the resistance of a conductor is _________ ____________ to the cross sectional area of the conductor - ANSWER: Inversely proportional How do we measure the amount of voltage? - ANSWER: Using a volt meter - it's used to measure the voltage between 2 points in a curcuit How do we measure the flow of charge? - ANSWER: Using an ammeter - it shows us how much charge is being pushed around the curcuit How do you find the gradient? - ANSWER: Increase in y/ increase in x AKA rise/run How would you find the total voltage if 2 cells in a battery are facing the opposite way? - ANSWER: The total voltage would be found by subtracting the 2 individual voltages How would you find the total voltage if 2 cells in a battery are facing the same way? - ANSWER: The total voltage is the sum of the individual voltages If the total voltage is 24V and there is one 2.0Ω resistor and one 4.0Ω resistor, find the current and voltage across each resistor - ANSWER: CURRENT: I = V/R, I = 24V / (R1 + R2), 24V/6.0Ω = 4.0A Voltage across 2.0Ω resistor: V = IR1, V = 4.0A x 2.0Ω = 8.0Ω Voltage across 4.0Ω resistor: V = IR2, V = 4.0A x 4.0Ω = 16V