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What is the electric current
Electric current is the flow of electric charges (usually electrons) through a conductor such as a wire.
Symbol and Unit of electric current
Symbol is I; Unit is A
Electron flow is in the _________ direction to the flow of current.
opposite
What charge does pass through 0.5 Ampere lamp in 200 seconds?
100 C
Ohm's Law formula
I=U/R
«A resistance of a conductor depends on factors:
length, cross-sectional area (thickness) and type of material; Temperature
If the cross-sectional area is doubled, what happens to resistance?
Resistance decreases
A wire has resistivity 2 × 10⁻⁶ Ω·m, length 3 m, and area 1 × 10⁻⁶ m². Find the resistance.
6
Properties of series combinations:
1. I=I=I; 2.U=U1+U2: 3. R=R1+R2
Properties of parallel combinations
1.U=U1=U2; 2. I=I1+I2; 3. 1/R=1/R1+1/R2
Why is a parallel connection is used in houses? Why is a series connection not used in houses?
Parallel: If one bulb burns out, the rest keep working.; Series:If one device breaks, the circuit opens → all devices turn off
Definition of Joule-Lenz Law
«hat electric current produces heat by passing through a conductor
Three resistors 2 Ω, 3 Ω, and 5 Ω are connected in series. a) Find total resistance b) Find current if U = 10 V
1) 10Ω; 2)1A
A 12 Ω and 4 Ω resistor are connected in parallel to 12 V. a) Total resistance b) Total current
1)R=3 Ω; 2) I=4A
In series circuits voltage is the same across all resistors. True or False
False
Increasing resistance increases current. True or False
False
