In the circuit shown in the figure, the voltage at both ends of AB is u = 8V and remains unchanged. If the voltage at both ends of R2 is U2 = 2V and R1 = 4 Ω, then the current through R1 is 0______ A. If the current passing through it is 0.4A, the voltage at both ends of the conductor must be adjusted to zero______ ．

In the circuit shown in the figure, the voltage at both ends of AB is u = 8V and remains unchanged. If the voltage at both ends of R2 is U2 = 2V and R1 = 4 Ω, then the current through R1 is 0______ A. If the current passing through it is 0.4A, the voltage at both ends of the conductor must be adjusted to zero______ ．

According to the voltage law of the series circuit, it can be concluded that: U1 = u-u2 = 8v-2v = 6V; & nbsp; & nbsp; & nbsp; & nbsp; then the current through R1: I1 = u1r1 = 6V4 Ω = 1.5A; & nbsp; & nbsp; & nbsp; & nbsp; because the current of the series circuit is equal everywhere, the resistance value of I2 = I1 & nbsp; & nbsp; & nbsp; & nbsp; R2: R2 = u2i2 = 2v1.5a = 1.3 Ω; & nbsp; & nbsp; & nbsp; & nbsp; the voltage at both ends of R1: U1 ′ = I ′ R1 = 0.4A × 4 Ω = 1.6V; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; R2 voltage at both ends: U2 ′ = I ′ R2 = 0.4A × 1.3 Ω = 0.52v; & nbsp; & nbsp; & nbsp; at this time, the total voltage at both ends of the conductor: u ′ = U1 ′ + U2 ′ = 1.6V + 0.52v = 2.12v

There are many streetlights on both sides of the street. They light up at night and go out in the morning. It seems that they are connected in series. But from what phenomenon can we judge that they are actually connected in parallel?

If one lamp breaks down, other lamps will not be affected, so they are in parallel
If it is in series, then one light is broken and one line is not on

&What does it mean in VB

It has two meanings
1. Represents the connection of strings, for example:
dim a as string
dim c as string
dim b as integer
a="abc"
b=123
c=a & b
Then, the value of C is "abc123"
2. Used after a variable or constant to indicate that the variable or constant is a long integer
123 & long integer constant
X & 'long integer variable